My SL175 look alike project.

ancientdad said:
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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This is all terra nova to me and pretty interesting. I wonder what you'll find inside.
 
Engine out and into the shed in less than 2 hours, taking it quite leisurely. Engine comes out easily by lifting at the rear to free the rear mounts, then leaned and twisted to the right, must try to recreate those moves when it goes back in.
 
OhioBackRoad said:
Hi Richard, I'm on the fence about putting an electronic ignition on my 175. What's your thoughts?
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I've had Charlies ignition for the best part of 10 years now, and it still works. Probably done 10K miles, moved around between several 175 engines. It just means no points to adjust, condenser to fail, doesn't seem to make if 'go faster' or start better.
 
ancientdad said:
I'm curious to see what you find, Richard.
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I've just taken the top cover off the cylinder head. On first look, everything looks fine in there. No end float on the cam to account for the noise I heard. Cam timing is correct. Turning the motor over with the plugs out, no odd noises or resistance. Only obvious problem is one clean plug, one black plug. Both exhaust pipes got hot when it was running, so both cylinders obviously firing.

I'm in two minds now. Was I just worrying about a carb problem ? That said, I've never heard noises like these from a 175 engine before.

I've got this far, might as well bite the bullet and lift the head.
 
Richard Pitman said:
I've just taken the top cover off the cylinder head. On first look, everything looks fine in there. No end float on the cam to account for the noise I heard. Cam timing is correct. Turning the motor over with the plugs out, no odd noises or resistance. Only obvious problem is one clean plug, one black plug. Both exhaust pipes got hot when it was running, so both cylinders obviously firing.

I'm in two minds now. Was I just worrying about a carb problem ? That said, I've never heard noises like these from a 175 engine before.

I've got this far, might as well bite the bullet and lift the head.
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Interesting that nothing is visibly obvious.

Your phrase in bold above struck me this morning and after thinking about it, there must be some correlation to an expression I've heard and used since a young age - "I've got half a mind to...." when you have conflicting thoughts and consider taking one approach. :giggle:
 
Well, nothing obvious springs to light. Plenty of oil in both cam journals, no more wear on bearing surfaces than was there already ( looks worse in photo than to my naked eye ), everything comes apart and goes back together without binding. There IS some endfloat on the cam, but I think this is usual in the 175 engines, cam chain seems to centralise things. So I'm going to reassemble and try again. No evidence of valves hitting pistons, though with correct valve timing that could not happen anyway. There is that dowel that I've omitted from the CD 175 cam, end slotted to drive the tacho mechanism. But I'm running another modded CD175 cam in same configuration in another engine, and it doesn't make that noise.

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May be wrong here but the piston picture appears to show intake valve contact and the valve pictures do as well. Are the valves the same size between engines?
 
Same valves used in CB200 as in the 175 engines. Different valve guides ( top hat valve seals on all four valves, as opposed to the 175 seals on exhausts only ) and springs. I think the marks in the carbon on the piston crowns are misleading, just carbon knocked off by my careless handling. I do plan to fill the combustion chambers with denatured alcohol to check for leaks.

Must admit, the photo of the combustion chambers does appear to show a suspect area on the edges of both inlet valves, will inspect again. It would account for the clattering noise. Still doubt this though, I'm that Lukes build over on Do the Ton used a CB200 head without issues.

Allen Millyard makes it all look so easy ........
 
Using clay to check crown, squish zone, valve edge clearance, is an old trick.
A thicker head gasket may be easier than cutting crowns or valve cutouts.
Was the head ever surfaced?
 
I've made a start on putting together a spare CB175 head, to see if the noise goes away when that is fitted. If it does, guess that's the answer, if not, problem lies deeper in the works :(

I say 'made a start', we spent yesterday evening in our local A&E department ( Emergency Room in the US ?), wifes leg gave way with a nasty cracking noise on her way upstairs. I was worried that it was an osteoporitic fracture, but A&E practitioner assures us that it is a torn calf muscle. Seems very painful and has largely immobilised her, so I am head cook and bottle washer, not to mention zoo keeper and dog walker, for the next (hopefully ! ) few days.
 
Richard Pitman said:
I say 'made a start', we spent yesterday evening in our local A&E department ( Emergency Room in the US ?), wifes leg gave way with a nasty cracking noise on her way upstairs. I was worried that it was an osteoporitic fracture, but A&E practitioner assures us that it is a torn calf muscle. Seems very painful and has largely immobilised her, so I am head cook and bottle washer, not to mention zoo keeper and dog walker, for the next (hopefully ! ) few days.
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Oh that does sound painful, I certainly hope things heal up quickly. we have enough random aches and pains at this point in our lives as it is, no need for any unexpected additions.
 
I got the 175 head fitted this afternoon. Usual faff getting the cam chain to engage with the crankshaft sprocket, until I had the bright ( to me ) idea of putting a spirit level onto the cylinder head. With the engine sat perfectly level on my bench the cam chain slipped into place almost straight away.

Riveted up the hollow pin cam chain link using the modified final drive chain tool, very easy and satisfying. Just need to finally torque the head and set the valve clearances now.
 
I found an SL350 rear light assembly at an online breaker. According to CNMSL, this part (84701312673XW) only fits the SL350. However, CNMSL also list the very similar part number (84701313673XW) for the SL175 and SL70 rear light assembly, so I bit the bullet and made an offer, which has been accepted.

Sure I can make it fit, got to be better than the one I made earlier. Uses a genuine SL175 lamp assembly on a generic bracket.

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Well, isn't a small world. I was looking on line for photos of SL350's, to compare the rear light with the SL175 part, when I came across this.


The Chris Skellern Collection. Chris is the chap who gave me a test ride on a Honda Hornet, when he was a salesman in the family firm, Skellerns Motorcycles, resulted in a sale. I knew he had a few old Hondas, he used to keep a couple on the showroom floor, one being a CB350/4, a bike I've liked the look of. They lost the Honda franchise a while back and became a Yamaha dealer. That dealership morphed into a Kawasaki shop, but that closed recently, showroom stands empty.
 
I ended up with an SL 350 K2 rear light assembly. It's not quite the same as the SL175 part, or indeed some other SL 350 models, based on pics found online. But the main thing is that the four mounting holes line up exactly with the holes in the SL 175 rear fender, and the angle of the light, ie perpendicular to the road, is correct. I have to adapt the SL175 light unit to fit the SL 350 bracket, as the 350 light is much larger. Whatever, it'll look more original than what I have fitted previously, and may confuse some future rivet counter :geek:

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For reference, a genuine SL 175 K1 lamp looks like this:

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And this is an SL 350 K2

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And finally, this another SL 350, version unknown, that appears to have same bracket as the SL175 K1

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Richard Pitman said:
I ended up with an SL 350 K2 rear light assembly. It's not quite the same as the SL175 part, or indeed some other SL 350 models, based on pics found online. But the main thing is that the four mounting holes line up exactly with the holes in the SL 175 rear fender, and the angle of the light, ie perpendicular to the road, is correct. I have to adapt the SL175 light unit to fit the SL 350 bracket, as the 350 light is much larger. Whatever, it'll look more original than what I have fitted previously, and may confuse some future rivet counter :geek:

For reference, a genuine SL 175 K1 lamp looks like this:

And this is an SL 350 K2

And finally, this another SL 350, version unknown, that appears to have same bracket as the SL175 K1
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Yes, the SL175K0 and SL350K1 both used the same size taillight assembly, and the SL175K1 used the same larger taillight (and wider bracket as required) as the SL350K2. The smaller earlier version was also used on the earlier versions of the SL100 and SL125, while the later versions of those as well as the XL250 used the later wider version taillight.
 
Put the engine back into the frame this afternoon, after all other domestic chores done. It went in easy as anything, can't think why I struggled last time. Just a matter of going in at the right angle and degree of twist. Still had a battle with front engine mounts though. I wonder now if the engine plates are supposed to be bolted the engine prior to lifting into the frame. In my case, the addition of a starter motor might make that difficult.

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The CNMSL fiche shows the engine bolts (15) going in from the left hand side, which would certainly make it easier to get nuts onto the other ends. However, the alternator side of the engine gets in the way of inserting the upper bolt from that side.

As an aside, the blurb on the CNMSL site states that the SL175 engine has lower 1st, 2nd and 3rd gear ratios. Not true, if the Honda FSM is to be believed. Overall final drive ratio IS lower, but that of course includes 4th and 5th as well. Maybe just lost in translation ...

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Richard Pitman said:
As an aside, the blurb on the CNMSL site states that the SL175 engine has lower 1st, 2nd and 3rd gear ratios. Not true, if the Honda FSM is to be believed. Overall final drive ratio IS lower, but that of course includes 4th and 5th as well. Maybe just lost in translation ...
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So many wives' tales out there about alleged specs, this site says the SL175 has a 2.75-21 front wheel/tire. No mention of the transmission ratios in their text, but the Cycle World review shown on the lower part of the page quickly disputes the front wheel size.

1970 Honda SL 175

Motorcycle Specifications Overviews and Road Tests
www.motorcyclespecs.co.za www.motorcyclespecs.co.za
 
And finally. Back down at the garage this afternoon. Refitted the over wintered battery, hooked up my lawn mower fuel tank via a tee piece, and fired it up. Still a bit mechanically noisy but I'm sure that refitting the fuel tank and putting in my new ear plugs will deaden the racket a bit. Slackened off the two rear head nuts, oil gushes out on both sides. Tacho works, so my slotted end CD 175 cam engages OK with the tacho drive. Lifted the tappet covers, plenty of oil on the valve spring caps. so I'm happy it's all getting well lubed.

Made a start on refitting the fuel tank. It is very crowded under the SL175 tank, hardly any clearance for the cross over line, spark plug leads, cam cover breather hose, throttle cables. Scratching my head about best route for fuel hoses from carbs to fuel tap, so gave up and came back here for a cup of tea. Wincycles carbs fitted, so there's the ugly business of the right handed left carb, if you see what I mean. Must have a look at some photos to see what I did last time around.

EDIT Found a photo from last year. This hose routing worked OK back then,

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Something is not right. Engine is very mechanically noisy. It makes good power right up to 10k and beyond, I've been for a test ride and deliberately rode it hard, figuring that if it was going to blow up it would best happen within pushing home distance.

Now, the noise does seem to emanating from the tacho drive area, but that could of course be my imagination, because that's the area I've modified by notching the end of a CD175 camshaft to drive the SL 175 tacho. The SL/CB/CL cam is counterbored at that end to take a 12mm knock pin, which engages with the centre of the tacho drive mechanism. I don't have this part fitted as the CD cam does not have the required counterbore.

Before pulling the engine out yet again, I'm tempted to fit a new CD 175 cam journal, see if doing away with the tacho drive quietens things down. Hopefully I'll be able to do this engine in frame, if I slacken off all the tappet adjusters. First pic below shows a CB and a CD cam, second shows CD cam with tacho drive notches filed into it.

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Removed the tacho drive and fitted the CD175 right hand cam journal in its place. Before removing the tacho drive I completely removed all four tappet adjuster screws and locknuts, to reduce the 'pull' on the camshaft. This worked well, new cam journal slipped into place easily, no force involved.

Valve clearances reset, engine started. Still mechanically noisy, probably quieter than before. It's running a new cam chain and tensioner assembly, so I'm guessing it's just a consequence of using a selection of used parts. I did select the best set of four rockers from the ones I have accumulated, cam lobes are good with no pitting. Plenty of oil up in the top end, I removed a valve cover with the engine running and saw plenty of oil flying about. New five part piston rings in honed bores, good compression ( judging by feel on kickstart, direct comparison with other 175 engines in the stable) right from the word go. No oil smoke.

Just going to run around on it for a while, see how it goes. Fingers crossed.
 
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