My SL175 look alike project.

Thanks. I didn't need to make a gasket after all, I just fiddled around with those gears for a bit more and then suddenly the end cap of the motor dropped snugly into position, screws fully tightened and the motor runs perfectly.

Ordering things in haste without checking part numbers properly, I now know that the CB250G5 uses the same starter motor and chain, but a different sprocket. Correct one on the way now, the G5 sprocket is too thick, raised edges either side of toothed area. I did think about a bit of grinder surgery, but easiest to use the correct part.

It also occurred to me last night that I have some used cam chains somewhere, I could have used a piece of that to make up the starter chain, a bit of slack due to chain wear wouldn't be a bad thing for the starter chain.
 
Cb200 (same as 175 ) starter sprocket arrived and fitted. Starter chain still tight as a bowstring when mounting screws fully tightened, but a few washers under the mounting points sorted that out. Alternator cover now fits correctly and the starter spins the motor over a treat. Plenty of Hondabond to hopefully prevent any oil leak from my slightly sloppy bored hole. If I ever did this again, I'd used a 45mm rather than 46mm hole saw.

Only part missing is the ? keeper that stops the stator gear moving outwards. Not sure what this actually achieves in practice, all seems to work OK without it.

This bit:
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And I believe the cover has a short stub of tubular casting that sits right next to the end of the starter motor shaft that would prevent it from moving very far at all, I know the 450 cover does.
 
ancientdad said:
And I believe the cover has a short stub of tubular casting that sits right next to the end of the starter motor shaft that would prevent it from moving very far at all, I know the 450 cover does.
Click to expand...

Yes, it fits snuggly against the starter motor sprocket, this was what was preventing the cover from sliding fully home when I had the incorrect (fatter) sprocket fitted.

Can't find a photo of the 175 case, but the CB200 has the same casting internally. ( Different shape externally)

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The engine with the new electric start is now relegated to the shed, waiting to be mounted into my spare 175 frame for testing later in the year.

Meanwhile, the SL175 is running around on the rebuilt electric starting CB175 engine. I'm using some original CB175 clocks on this bike, which don't have a trip meter to remind me when to refuel. So I've sourced some CB200 clocks, which do have the trip, and also look better, in my opinion, angled toward the rider, with full chrome backs.

I'm running an aftermarket flasher relay and LED turn signal and repeater lamp. There are several issues with this setup. If you just fit LEDs to the turn signals, you may find that all four signals illuminate and flash too rapidly when either side is activated. A cheap aftermarket LED turn signal relay sorts out the flashing rate.

However, there is still a problem, centered on the turn signal repeater lamp. This uses an incandescent lamp, which lights up no matter which way the current flows. It is wired to both legs off the turn signal circuit, and with the standard turn signal bulbs and relay illuminates when either the orange or blue wire becomes positive, finding ground through the other side of the circuit. With LEDs in the turn signals, the opposing side also illuminates as only a small current is required to operate them.

A further issue arises if an LED repeater lamp is fitted. LEDs are polarity limited, thus will only illuminate when current flows in correct direction. On my bikes, the orange wire needs to be +ve for the LED to work.

Both issues are solved by fitting diodes to the incoming blue and orange wires, taking both to the positive side of the repeater bulb holder. The blue wire from the ground side of the bulb holder is then connected to the green ground circuit. I used some N4007 diodes that I had lying about. I've used these in the past and they still work, so I assume these are OK. They are tiny, same diameter as the wiring, so are easily hidden inside heat shrink insulation. The green earth wire can be butt jointed into the green ground wire from the instrument back light, so once everything is insulated and tidied up the wiring emerging from the back of the tacho appears completely stock, and will function as such, with the original relay and lamps.

A picture is worth umpteen words, excuse my scribble.

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CB200 clocks now fitted, so I now have a working trip meter.

Bit more work involved than anticipated. CB200 clock mounting bracket fits neatly onto existing CB200 top yoke, all looks factory in that area now. However, the SL175 clocks sat quite a bit higher on a raised bracket, and the lower CB200 clocks fouled the headlamp. I had previously made a set of headlamp ears that sat the headlamp lower, in the CL 175 position, so I swapped the fitted ears for the earlier pair.

Of course, this involved removing the front wheel and fork legs, along with the top yoke. This did give me the opportunity to repair one of the M6 fender mounts, stripped by a PO of these CD250u forks. Drilled and tapped to M8 now.

Hadn't noticed until I looked at my photos, headlamp is aimed at the sky, odd that this isn't so noticeable just stood by the bike. And the tacho cable is now too long. The CB/CL and SL all have the same part number for this cable, so I think that on the real SL175 the extra length is taken up in the raised clock position. It'd be nice to find a shorter cable from another Honda model.

Anyway, it's getting there, conversion from off road bike to street bike.

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Richard, I suspect a 350 tach cable would fit if it measures shorter, the ends seem to be the same.
 
Also Richard, as you sure the cable you have is the original length? It may have been replaced by a PO during its life with an incorrect copy. (y)

(Bike looks great, by the way!!)
 
Remember, this bike was built from a pile of spare parts, so that tacho cable was an aftermarket part purchased by me, advertised as a CB175 part. I'm fairly sure that I compared it for length against the OEM tacho cables fitted to the CL and CB 175 in the garage.

Good news is that the 'new' clocks work fine, bike is running well, pulling an indicated 70mph up hill this afternoon, albeit with a slight following wind.
 
I took delivery of this tacho cable today. Listed as a CB250/350 part, it turns out to be identical to the OEM tacho cables on my CB and CL 175s, grey outer, 60cm/2ft long. Made in Japan, by <sic> 'Mitsobosho'.

Tacho Rev Counter Cable Honda CB250K CB350K CB250 CB350 K3 / K4 / K5 Pattern | eBay

Same vendor lists a CB/CL/SL 175 cable, but that has a black outer and costs a couple of quid more.

CMNSL has different part numbers for the 175 and 250/350 cables, but just looking at the pictures I reckon several different '70's Honda cables would also fit.

EDIT Just need to find a grey speedo cable now ...
 
First oil change yesterday, 500 miles on this engine.

Warmed engine, oil catch pan in position, sump plug removed, oil everywhere. The gap in the sump guard / bash plate is wide enough to get a 19mm socket onto the sump plug, but is narrower than the diameter of the plug, so oil drains onto the inside of the bash plate, and then dribbles all over my garage floor. Nice design Honda.

Bit like an elderly man at the urinals ....
 
Richard Pitman said:
First oil change yesterday, 500 miles on this engine.

Warmed engine, oil catch pan in position, sump plug removed, oil everywhere. The gap in the sump guard / bash plate is wide enough to get a 19mm socket onto the sump plug, but is narrower than the diameter of the plug, so oil drains onto the inside of the bash plate, and then dribbles all over my garage floor. Nice design Honda.

Bit like an elderly man at the urinals ....
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“You learn something new every day “ as the saying goes, yet I don’t always like the lesson. :sad: The urinal I can identify with being of a certain age too.
Good to know though as my CL77 and CL175 both have those bash plates.
 
First ride of the year today. Pumped up the tyres, refitted the battery, oiled the drive chain, turned on the fuel tap and let the emptied float bowls fill. Started third press of the button and off we went, short ride to a friends place.
 
Richard Pitman said:
First ride of the year today. Pumped up the tyres, refitted the battery, oiled the drive chain, turned on the fuel tap and let the emptied float bowls fill. Started third press of the button and off we went, short ride to a friends place.
Click to expand...

It's always good when things pick up right where they left off before the winter nap.
 
I've just got hold of the SL175 K0 owners manual, the little book that sits under the seat.

I was hoping that it might reveal a few secrets, such as that removable plate on the underside of the exhaust ( spark arrestor cleaning ?? ), but no joy. In fact, most of the booklet appears very similar to the CB175 handbook, including shots showing CB chrome exhaust headers. Bit disappointing, but I'll fire up my scanner in the next few days, make it into a pdf for the library, if anyone needs it.
 
Richard Pitman said:
I've just got hold of the SL175 K0 owners manual, the little book that sits under the seat.

I was hoping that it might reveal a few secrets, such as that removable plate on the underside of the exhaust ( spark arrestor cleaning ?? ), but no joy. In fact, most of the booklet appears very similar to the CB175 handbook, including shots showing CB chrome exhaust headers. Bit disappointing, but I'll fire up my scanner in the next few days, make it into a pdf for the library, if anyone needs it.
Click to expand...
We always accept more info into the library.
 
Richard Pitman said:
I've just got hold of the SL175 K0 owners manual, the little book that sits under the seat.

I was hoping that it might reveal a few secrets, such as that removable plate on the underside of the exhaust ( spark arrestor cleaning ?? ), but no joy. In fact, most of the booklet appears very similar to the CB175 handbook, including shots showing CB chrome exhaust headers. Bit disappointing, but I'll fire up my scanner in the next few days, make it into a pdf for the library, if anyone needs it.
Click to expand...

Thanks for the offer Richard, you can email it to me or Jim and we'll get it into the library. Pretty sure we don't have one for the SL.
 
I've been out on the SL175 alike quite a bit recently, whilst our current spell of nice weather lasts. Just riding around the local back lanes at 30-40 mph, with the occasional 70mph blat on the wider bits. Still running really well, and really comfortable to ride. Lightweight and low seat, easy to wheel about. Can't help fantasising about fitting a disk braked front end, better rear shocks and a stronger engine, just dreaming really.

A pic from this afternoons ride, unusual local church at Pirton. Timber bell tower added at a later date to the original stone built structure, then they had to add those timber buttresses, as square tower couldn't cope with the bells swinging about. Must be a motorcycle similarity, adding balance shafts to a 180 crank engine ?

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^^^Or even a 360° crankshaft like the CB400N, but I see what you mean about the bells probably swinging left/right/left/right in tandem.
 
I have stood at the top of the tower of Worcester cathedral when the bells are being rung. The cathedral is an immensely strong and heavy stone structure, but I swear that I could feel movement beneath my feet when the bells pealed.

Worcester bridge and cricket ground

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A long way down !

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Quasimodo and friends ?

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Thanks for those pictures Richard, you don't get the true feeling of the height of the tower from the ground-level pics.

I can envision the bell ropes lifting them off the floor (or that box the person on the left is standing on).
 
I decided that I didn't like the look of that low front mudguard ( fender ? ) on my SL175, so I've reverted back to the high mounted version. Lovely weather for a ride around the local lanes today, brief halt at Pershore to shake something out of my ear. Not sure if it was an insect or wax dislodged by the vibrations !

Got chatting to a chap who admired my bike, wasn't aware of the existence of the SL 175 variant. Turned out that he was also a bike enthusiast, currently rebuilding a Yamaha DT125, along with various other bikes in his stable. Also informed me that there will be a bike night at August Bank Holiday Pershore Plum festival.

Another gratuitous pic of my bike. Spot the VHT sticker.

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Sticker is on the back of my Bell open face helmet, the lid that I usually wear while riding the little bikes. Face gets pebble dashed by insects and road debris but it's worth it. I do wear an Arai full face when out on the 600.
 
First bike ride of 2024 !

UK weather has been so blooming miserable, wettest Spring on record. Finally had a warm dry day yesterday, so put the battery back on the Sl175, pumped up the tyres, topped up the fuel, oiled the chain and checked the dipstick, then off out for a 35 mile spin around the lanes. Had to make a diversion at Upton on Severn due to a flooded road.

Time to wake up the other three now, I suppose. :giggle:
 
Hi Richard,

Your SL175 looks great!

At your convenience, can you tell me if it has some type of a rear sprocket shield or chain-keeper of sorts? I ask because it does look useful and I was interested in having the same for the SL175 project I am looking forward to working on.

Thanks!
Dan
 
Thereby hangs a tale. My 'SL175' is built from a collection of parts, and my rear wheel assembly is from a CB200, swingarm from a CB175. There is minimal clearance ( on m bike ) between that sprocket thingy and the inside of the swing arm, in fact I had it rubbing at one stage, took a while to find out where the noise was coming from. My CL175K7 has the same setup as stock, and there is plenty of clearance.

I would remove it if I could, but it acts as a spacer under the big circlip that holds the sprocket on, comes a package with the CB200 / 175K7 rear wheel and sprocket, which also uses the heavier chain. I don't think it would be a retrofit with the earlier parts.

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This bike is currently running a rebuilt CB175 engine. I now have the correct ( engine numbers match the registration document ) SL175 engine almost ready to be swapped back in.

As this bike is a 'bitsa', the engine is no different. Standard SL175 bottom end, with an electric starter grafted on. It didn't come with a top end, so it has usual 175 cylinders and pistons, but the head is from a CB200.

At risk of repeating myself, but here goes. The CB200 head has the same combustion chamber volume and same valves as the 175. Compression ratios are the same, 200 has lower domes on the pistons. EDIT Head gaskets are NOT the same. ( Use 175 gasket with 200 head and 175 cylinders ) The 200 has better valve guides, with proper top hat stem seals on all four valves. According to a thread I read years ago on 'Dotheton.com', Zekes bikes, the 200 head has better porting. Can't see a difference myself. It also has an extra row of cylinder fins, more of which in a moment.

To keep with the bitsa theme, I have fitted CB175 cam journals, with a CD175 cam, notched to work with the CB175 tacho drive. Oil feed drilled in the head to feed the points side cam bearing.

And here's a minor snag. The extra head fin clashes with the CB175 points side housing. ( CB200 has a different shaped housing ) Few seconds with an M8 drill bit and an extra grommet sorted this problem.

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I've never thought about this until today - quick search shows the 200 engine has a 55.5mm standard bore, 175 is 52mm. Generally anything over 1mm larger needs a different head gasket, does Honda get away with it on this engine because of the shape of the piston domes? Never touched a CB200 engine internally prior to leaving the Honda world.
 
Yes, the CB200 pistons have a flat rim. The CB200 head gasket is obviously larger, but the 175 gasket fits the 200 head when fitted to 175 cylinders. Large flat area around the combustion chamber.

EDIT Just re read what I wrote earlier "head gaskets are the same" - clearly not thinking at that moment

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Thought I'd have a look at the noisy starter clutch while engine was in the shed. Should be a quick simple job I thought. Except I cannot undo the bolt that holds the alternator rotor on. These usually pop straight off with the battery impact gun. No luck, so dug out the mains electric impact. This is just spinning a 12 point socket on the bolt head, so I stopped before damaging the bolt beyond hope. Amazon Priming a 14mm and 13mm 6 point 1/2" sockets, should be here sometime tomorrow. The rotor in question has been on and off several times before, can't imagine why the securing bolt has got so tight. Heat probably not a good idea where magnetism is concerned.
 
The alternator rotor securing bolt seems to be a rare part. CNMSL has a couple of new ones, but I can't find any locally at sensible prices. This despite this bolt being common to a lot of Honda models. Any reason why a normal bolt and a large washer could not be used as a substitute ? Unusual thread pitch ?

( I haven't destroyed this one yet, and I also have a spare one in another engine, so I'm more curious than desperate ).
 
The flange head is one reason but not likely overly important. But the little divot in the bolt head is for the mechanical tach that connected to the dealership's service tester for bikes that didn't have a tach during tune-up needs.
 
6 point 14mm 1/2" impact socket did the trick, Clarke mains impact tool whipped it straight out, no drama. Rotor came off easily using same tool. Then some fiddling and swearing fitting the starter clutch repair kit, got there in the end. Flushed out loads of muck from the assembly using brake cleaner, prior to rebuild. Quick bench test had the starter turning the motor over easily, without the previous nasty noises. Noticed that the circlip on the gear change shaft wasn't seated properly, took the opportunity to fix that. Cover back on with new gasket.

The 4mm head washers were a fail, not enough free stud thread left for torquing down properly, so reused the rusty originals. Just needs valve clearances and ignition sorting now, then ready to refit to SL175.

Other nice thing about the CB200 head is the longer spark plug threads. Got to be good for cooling and sealing, also less chance of knackered threads. Just need to remember not to put these spark plugs into a 175 head. :eek:
 
I took the SL175 exhaust off yesterday. Should have done this earlier in the year, when it was still hot outside, unlike current monsoon conditions. It needs sanding down and recoating in black HT paint, which needs heat to cure nicely.

Idle hands got the better of me, and I removed the little cover on the underside of the exhaust can, next to the stamped writing about 'spark arrestor'. No mention in the handbook about this as a maintenance item. I wondered if this area filled up with soot, requiring periodic emptying, but it seemed clear in there. Now I have a snapped off screw to deal with. JIS screwdriver gripped hard enough that screw snapped off before the driver lost its grip in the screw head.


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Got the seized screw sorted out OK. Found a rust hole that I'm sure wasn't present when I fitted this system a few years back. Luckily, rest of muffler is solid, and seems to be made of thicker metal than most systems of that vintage. I really must practice my welding. First bead of weld went very well, down hill after that. Still, it's done the job, no one will see it there, tucked behind the can. Spent the rest of the afternoon starting to clean the headers back to bare metal, started out doing it by hand with 60 grit abrasive paper, soon gave up and reverted to flap wheel in the angle grinder, followed by the power file.

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Finally got around to taking out the CB175 engine, ready to refit the rebuilt SL175 engine.

Very surprised to find that all the engine mounting bolts were loose. Either I had a senior moment during the initial build, or they have worked loose in service. All nuts are aftermarket nylocs, so none had actually come undone, just loose.

It has given me the opportunity to 'repair' one of the front engine mountings, the thread in one of the integral 'nuts' was very worn, so I sliced it off with the angle grinder and tack welded an M8 nut in place. Not without issues, discovered that I had no gas in my Mig welder, so I dug out the cheap Aldi / Parkside arc welder that I bought ages back and never really played with. This actually worked well, and I think that I will get some more rods for it and experiment with it. I think that I was initially quite apprehensive about using the thing, but I have since got quite blase about welding things and making sparks, having used the Mig welder quite a bit ( badly ! ), bought a proper welding helmet rather than the daft bit of smoked glass that came with the cheapy MMA welder.

I've taken the exhaust down pipes back to bare metal and resprayed with Simoniz heat resistant paint. Described on the can as matt black, but has actually come out as a rather nice satin black finish, interesting to see what it looks like after heat curing.

Putting the engine back in is on hold at the moment. Having spent an afternoon hunched over the SL175, I stood up and put my back out. Currently hobbling about, swearing a lot.

That bracket:

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Working carefully today. Transported the CB175 engine up from the garage to the shed. Pic shows it with Sl175 engine alongside and CD175 engine up on the work bench. Just debating how to run the starter cable as the SL doesn't have this option. On the last install, I cable tied the cable to the lower frame rail, keeping it well away from the exhaust and drive chain. I'm hoping to keep the cable in the standard position clipped under the sump this time, just need to check that the underslung SL exhaust pipes don't get too close

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Engine back in the frame now. As Jane Austen didn't say, in her book 'Jane Austen and the Art of Motorcycle Maintenance*', " It is a truth universally acknowledged that a single man in possession of a motorcycle finds it much easier to take it to pieces than he does to put it back together again ". Taken me two afternoons to get back to this stage, when it just took a couple of hours to pull it all apart.

Rerouted the starter cable much more neatly, was able to shorten it by about 20cms.

* I'm sure that there are plenty of other quotes in that non existent book that would apply to our hobby.

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Exhaust and sump guard fitted today. The left exhaust pipe does run quite close to the starter cable, possibly 3cm clearance. Most likely it'll be fine, but there is always the thought that I might stall the engine in traffic, hit the starter button then listen to the battery explode because the starter cable has melted and shorted out. Probably paranoia, however I'm thinking that I will wrap the exhaust pipe at that point with some of that stuff the 'custom' bike lot use to hide their rusty downpipes. It won't show on the SL, hidden under the bash plate.
 
Richard Pitman said:
Exhaust and sump guard fitted today. The left exhaust pipe does run quite close to the starter cable, possibly 3cm clearance. Most likely it'll be fine, but there is always the thought that I might stall the engine in traffic, hit the starter button then listen to the battery explode because the starter cable has melted and shorted out. Probably paranoia, however I'm thinking that I will wrap the exhaust pipe at that point with some of that stuff the 'custom' bike lot use to hide their rusty downpipes. It won't show on the SL, hidden under the bash plate.
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Might be a good thought, and something I might have to consider as well if I decide to put the electric start back on my red 450.
 
Wrapped the left exhaust pipe where it runs close to the starter motor cable, cable fitted in the 'official' CB/CL position, clipped between the fins on the lower crankcase. Now have itchy fingers, should have worn the gloves that came with the fibre glass exhaust wrap. Fiddly job, involved removing sump guard, lying full length on the garage floor ( no luxury bike lift here ). Impressed with the stainless steel ties supplied with the kit, very neat and secure, and all nicely hidden now the sump guard is back on.

Tyres pumped, chain adjusted and lubed, clutch adjusted. Just need to check Charlies ignition timing, refit the fuel tank and hopefully good for first start up.
 
Checked and adjusted the Charlies place ignition, then refitted the tank, after much cursing at the cross over hose and fuel lines, which seem even more constricted on the SL tank than on the CB / CL variants.

First startup. Disaster. When it did finally start, after many attempts, it did not run well. I've never heard so much mechanical noise from a 175 engine. It really didn't want to run, I could hold it at 2-3k, but it would die as soon as the throttle was released, even with the throttle stops on the carbs screwed in half a turn. Did this for a bit in the faint hope that something was stuck, no joy. So I'm afraid it's engine out time again.

I do have a complete spare CB175 engine, so I might swap the top end from that onto the SL bottom end. It'll be interesting to see what I've done wrong inside this motor. Off now to search online for some more cam chain soft links ...
 
Richard Pitman said:
Checked and adjusted the Charlies place ignition, then refitted the tank, after much cursing at the cross over hose and fuel lines, which seem even more constricted on the SL tank than on the CB / CL variants.

First startup. Disaster. When it did finally start, after many attempts, it did not run well. I've never heard so much mechanical noise from a 175 engine. It really didn't want to run, I could hold it at 2-3k, but it would die as soon as the throttle was released, even with the throttle stops on the carbs screwed in half a turn. Did this for a bit in the faint hope that something was stuck, no joy. So I'm afraid it's engine out time again.

I do have a complete spare CB175 engine, so I might swap the top end from that onto the SL bottom end. It'll be interesting to see what I've done wrong inside this motor. Off now to search online for some more cam chain soft links ...
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Sorry to hear Richard, and it's surprising to me because you've been in these engines often enough that you know them like the back of your hand. Hopefully it's nothing serious, just a shame it has to come out of the frame again.
 
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