Idle Tuning and more, CB450K project

[cellomaster]

I have just got my CB450K running and driving, its so much fun! That being said, it doesn't want to idle below 2K, and sometimes it'll get "stuck" at 4k, and by letting out the clutch a bit, i can pull it back down to 2k (and then pull the clutch again all the way, no I'm not burning my clutch ). I have a carb kit coming, where i will replace the gasket and seals after going through and cleaning every nook and cranny with carb cleaner and my ultra sonic cleaner. I also bought some new air filters, mine are not horrible, but not great either. My gas mileage is also kind of crap, roughly 100 miles on one tank. Fully loosening the idle screw only brings it to 2K, cant go any lower without physically moving the butterfly close.

My bike runs great, very responsive on throttle, easily hits 50-60, no problems. It struggles (or is at least slow) getting to 70 (and it sounds and feels like i'm going to break something), but that may just be the bike itself...?

FYI, I am only running non-ethanol gas, and the local stuff i have access to is NE 91. Although to start the bike originally I did use NE 87.

Would some new air boots help with this whole process? How would i know if i have leaky ones? Anyone have a supplier I could buy from?

Also, any tips on tuning would be helpful

Thanks!

 

[RobMan]

Please add some pictures of your bike. Does your bike have stock air filters or pods? You can check the intake boots by spraying a little carb spray where they connect to the head and the carbs. If the idle changes you have a leak. You mentioned only swapping the gaskets and seals so you probably know to use the stock brass and not the stuff from the kits. Take a hard look at everything. One cause of hanging idles on these bikes is the mechanical advance unit behind the points plate. They get dirty and need to be cleaned and the springs get weak as well.
My best advice is take it one step at a time, take lots of pictures and take advantage of the group knowledge here. Here is a link for a new to you vintage bike penned by @LongDistanceRider who is an admin here.

Basic Checklist for the New to you Old Bike

Note: this was originally written for the SOHC 400/450's so some information may not apply. Congratulations, you are the proud owner of a Vintage Honda Twin. One that may or not may have been maintained properly. Of course, the previous owner told you that everything is absolutely perfect and...

www.vintagehondatwins.com

 

[stl360+450]

+1 on Rob's advice.

Things to check:

• Make sure the timing is on the money.
• Look for air leaks at the carb tops, around the carb boots, near the air screws.
• Make sure the throttle cables are not bound up, preventing the throttle arms from resting the stops.

 

[boddy]

+1 on all of the above and make sure you follow the steps from the Factory Service Manual (FSM) and not some of the advice found in certain you tube videos. PM one of the admins for the FSM if you don't have one.

 

[ancientdad]

And though it is not always caused by loose advancer springs, before he sets the points and timing he should make sure they're in good condition and the advancer operation is smooth.

 

[ancientdad]

+1 on all of the above and make sure you follow the steps from the Factory Service Manual (FSM) and not some of the advice found in certain you tube videos. PM one of the admins for the FSM if you don't have one.

I've set up quick links to the commonly requested FSMs at the top of the FSM Library thread for easy access.

 

[cellomaster]

Please add some pictures of your bike. Does your bike have stock air filters or pods? You can check the intake boots by spraying a little carb spray where they connect to the head and the carbs. If the idle changes you have a leak. You mentioned only swapping the gaskets and seals so you probably know to use the stock brass and not the stuff from the kits. Take a hard look at everything. One cause of hanging idles on these bikes is the mechanical advance unit behind the points plate. They get dirty and need to be cleaned and the springs get weak as well.
My best advice is take it one step at a time, take lots of pictures and take advantage of the group knowledge here. Here is a link for a new to you vintage bike penned by @LongDistanceRider who is an admin here.

Basic Checklist for the New to you Old Bike

Note: this was originally written for the SOHC 400/450's so some information may not apply. Congratulations, you are the proud owner of a Vintage Honda Twin. One that may or not may have been maintained properly. Of course, the previous owner told you that everything is absolutely perfect and...

www.vintagehondatwins.com

Thanks so much, and thanks to the rest of you too, great advice. I have stock air filters right now, switching to pods. Will do on the carb spray. I have heard that the carb kits have crappy jets, so i'm planning on cleaning and reusing mine, especially since i'm having no major problems, just trying to tune better.

Sorry about no photos thus far, here are some!







(this was before some of my new parts like tires, coils, condenser, etc)

 

[RobMan]

Very nice! I wish my 450 had looked half that good when I got it. I would recommend keeping your stock filters on at least until you get it tuned properly and then swap to the pods but many folks here complain of poor running conditions with pods where they don't allow the piston in the CV carb to operate properly. Here is a link to where you can get repop filters at a reasonable price from Scrambler Cycle.

Honda 72-74 CB450 72-74 CL450 Air Filter Set Left and Right - Reproduction

Honda 72-74 CB450 72-74 CL450 Air Filter Set Left and Right - Reproduction See installation steps below.The 1971 and earlier CB450 and CL450 used a different style of plastic filter housing. These filters fit the original housing on the models shown below.Original filters for the 450's have...

scramblercycle.com

I have them on my 1972 build and I had to adjust the battery tray slightly to get the mounting holes lined up. BTW what is the condition inside the fuel tank? Rust can cause big problems with the carbs.

Again really good looking 450.

 

[boddy]

Nice clean bike. Is that a Triumph tail light?

 

[ancientdad]

Now you need a CL seat to match up properly with the CL tank. And these 3 things stand out to me immediately. Not so bad to be missing a points cover screw, but a cam bearing cover screw - 1 of only 4 in each - should be replaced right away. And the ignition switch seems to be rotated in the bracket, or you've turned off the bike by going to the Park position. And one last thing - when you use the correct 5.5mm Honda fuel line for these bikes, you don't need automotive-style clamps that distort the fuel line and often allow it to weep fuel.

 

[ancientdad]

I have stock air filters right now, switching to pods.

With nice condition stock sidecovers, why? These is zero performance gain (and often a loss of performance and rideability until you get the carbs jetted right), only the struggle of making the CV carbs run like they should with air filters not even close to the proper design they are designed to work with.

 

[cellomaster]

Not so bad to be missing a points cover screw,

Noticed this too...Any idea where I can get some OEM ones?

but a cam bearing cover screw - 1 of only 4 in each - should be replaced right away.

I did not notice this, so thank you!! Again, any idea where I can get some?

And the ignition switch seems to be rotated in the bracket, or you've turned off the bike by going to the Park position

Good to know...when it is horizontal, it is in park, 45 degree is on, and vertical (like how it is) is off.

 

[cellomaster]

With nice condition stock sidecovers, why? These is zero performance gain (and often a loss of performance and rideability until you get the carbs jetted right), only the struggle of making the CV carbs run like they should with air filters not even close to the proper design they are designed to work with.

Honestly...the cost. They may not be long term, but they are far far cheaper than a reproduction style filter. And the pods I got, I can still put my side covers on, so it looks 100% OEM. But my filters were pretty bad, so I needed new air filters, at least for the short term.

Doesn't seem to run much different after install, maybe a little more "poppy" at the exhaust, which i don't mind at all.

 

[ancientdad]

Noticed this too...Any idea where I can get some OEM ones?

If you have a Honda dealership nearby they might still sell them, plenty of metric bolt and screw places online too but others here might have better suggestions. I haven't bought any in so long I'm sure things have changed.

Good to know...when it is horizontal, it is in park, 45 degree is on, and vertical (like how it is) is off.

Sounds like the switch has been out of the bracket and put back in about 180° off. This is how it comes from the factory.

 

[boddy]

For your hardware you can check out this link. I used Partzilla in the past but screws and bolts are cheaper if you by them from Partzilla automotive.

Buying OEM Honda Hardware

Apologies if this has been covered before, but the conversation on rising parts costs we're all seeing made me want to share this: Being a landing spot for derelict parts from random bikes, I've had to cull together the proper hardware a bunch of times. While Bolt Depot/Grainger, etc are all...

www.vintagehondatwins.com

 

[cellomaster]

Sounds like the switch has been out of the bracket and put back in about 180° off. This is how it comes from the factory.

Is it a big deal if i leave it as it is...? I have gotten used to it LOL

For your hardware you can check out this link. I used Partzilla in the past but screws and bolts are cheaper if you by them from Partzilla automotive.

I appreciate this so much, thank you!!

 

[ancientdad]

Is it a big deal if i leave it as it is...? I have gotten used to it LOL

Of course not, that's up to you. That's just me wanting you to know how it was when new. I will tell you it would probably flummox the next owner for a minute if they're used to '70s Hondas.

 

[cellomaster]

Nice clean bike. Is that a Triumph tail light?

I honestly do not know, it is what came with the bike. I haven't done much research to figure out what (if anything) on the bike was swapped out.

 

[ancientdad]

I honestly do not know, it is what came with the bike. I haven't done much research to figure out what (if anything) on the bike was swapped out.

It does look like an aftermarket Lucas taillight copy.

 

[cellomaster]

Alright, i finally took off both carbs and cleaned them deeply and thoroughly. They work like a top now! Before, i maxed out around 9-10K rpms, couldn't really get above that, and now i can easily reach into the 12K. I know its not great for the internals to run that high for long, but it was a good sign that I had cleaned something correct.

Still need to tune the idle a bit better, balancing out the idle speed screw and the throttle cables is difficult...but, nothing an hour can't fix.

I used the rebuild kit from 4into1, but I kept with all my stock screws and jets, just used the included washers/seals/gaskets/etc. I tested my stock floats, and they weren't leaking, so i reused them, but I do also have the new floats. Lmk if I should put the new ones in.

I have two questions...first, this is what my air fuel screw looks like. Based on photos I am seeing online, this is not stock, this is a replacement screw from a PO. Can anyone confirm this? And would this be worth getting the proper OEM screw?



Second question...sometimes my carbs don't want to drop down to the idle (even tho its a bit high, 2k-ish). They will stay at 4K, and only after letting the clutch out and "manually" lowering the rpms will it stay at idle. This is the same issue i was having before cleaning the carbs. Why are they sticking?

Thanks guys!

 

[ancientdad]

Second question...sometimes my carbs don't want to drop down to the idle (even tho its a bit high, 2k-ish). They will stay at 4K, and only after letting the clutch out and "manually" lowering the rpms will it stay at idle. This is the same issue i was having before cleaning the carbs. Why are they sticking?

I'm not a carb guy, haven't touched a stock carb on a twin in decades so I'm no help there.

But as to the idle hanging, have you checked the timing with a strobe? Did you check the advancer for smooth operation and no slop in the return springs? If there is any free movement in the weights without spring return, this can cause a hanging idle even with clean carbs and everything else set dead on.

 

[tmross]

Second question...sometimes my carbs don't want to drop down to the idle (even tho its a bit high, 2k-ish). They will stay at 4K, and only after letting the clutch out and "manually" lowering the rpms will it stay at idle. This is the same issue i was having before cleaning the carbs. Why are they sticking?

I just went through this same thing with my CL350 rebuild last week. After reading around various forums I found a cb450 hanging idle thread somewhere and the problem ended up being intake valves adjusted too tight. So I checked my intake valves and they were indeed too tight, loosened them up and hanging idle problem was solved for me. However at the same time I adjusted the valves I also put some hondabond on the intake manifold gaskets as I suspected a possible air leak there, which can also cause a hanging idle. So I can't definitively say if it was the valves or the leak that was the problem, but it was likely one of them, so check both.

 

[cellomaster]

But as to the idle hanging, have you checked the timing with a strobe? Did you check the advancer for smooth operation and no slop in the return springs? If there is any free movement in the weights without spring return, this can cause a hanging idle even with clean carbs and everything else set dead on.

Good idea...and no, i have not. Is it ok to have that cover off while running? Last time, a bit of oil came out when i took the cover off.

Did you check the advancer for smooth operation and no slop in the return springs

Excuse my ignorance...how do i do this?

 

[ancientdad]

Good idea...and no, i have not. Is it ok to have that cover off while running? Last time, a bit of oil came out when i took the cover off.

Yes, though it's advisable to put the bike on the centerstand and slip a block of wood under the left side of the stand to lean the bike to the right slightly, it helps minimize the oil spray when checking the dynamic timing with a strobe. With a known good advancer unit in proper working condition, you can set the timing statically with a test light but it's always advisable to confirm full advance timing with a strobe for best all-around performance and rideability.

Excuse my ignorance...how do i do this?

The advancer unit is behind the points plate. When you adjust the points gap, you are working with the points cam lobe on the advancer unit when you rotate the engine to the maximum points opening position to adjust the gap. When you remove the points plate to inspect the advancer and its operation, this is what you'll see. (courtesy @stl360+450) Remove the 6mm (10mm head) bolt from the end of the camshaft and the advancer should slide right off the end of the cam. Be cautious with the 6mm bolt, and don't use it to attempt to rotate the engine or it will break off (turn the engine at the crankshaft with a 14mm wrench once the alternator rotor/timing cover is removed).

 

[ancientdad]

Here's a lot more reading on the subject

Ignition Advancer Rebuild Information, all 450/500T Models

I wrote this and posted it on another site. They're being annoying just now so am bringing that post over here. I believe everyone can benefit from this information. I learned it the hard way. Please feel free to post your experience(s) too. Part 1 (of 2) There are three ignition advancers...

www.vintagehondatwins.com

 

[cellomaster]

New question...

I was polishing all my chrome today (it is very nice now), and I noticed a discrepancy between my two exhaust baffles. Would this greatly affect the performance/tuning/idling/etc, and would it be worth it to drill some of my own holes? I do notice that the right side has more pressure coming out, and the left side has gotten a bit warmer (based on discoloring at the front of the exhaust line).

Left side:


Right side:

 

[cellomaster]

Well...I think I sent err a little too hard! I have a big split (definitely a split, lots of exhaust gets out) along the ridge, right under the passenger foot peg. Do y'all think I should replace the full pipe, either from the unspoken in Houston or from eBay, or should I do some sort of exhaust paste and just refill it and maybe some touch up paint?

Also, why would this have happened? It is only on one pipe, on the right side, and its 8ish inches long? I definitely ride the bike, sometimes fairly spirited, but I wouldn't say I'm killing it, or letting it overheat.

 

[stl360+450]

It must be pretty crusty on the inside. Otherwise, I would suggest having a good welder look at it, but it might be too thin for that option.

 

[cellomaster]

I talked about this a little bit in a different thread, but my cb450 K5 could not really max out where it should have. On the top end, it couldn't get past 80 on a good day, and it really just sounded like it was bogging down at full throttle. On recommendation, I have worked on re-timing the points according to the FSM. After setting both gaps, I adjusted the plate so that left and right cylinder fire on mark. She certainly idles better, but riding is nearly impossible. Very low acceleration, and it sounds like it's getting bogged down the entire time. I only adjusted the gaps slightly, the main thing I changed was the plate. Below is where my current plate setting is. Any thoughts?

 

[EzPete]

How does the advance mechanism look? It sounds like it's not advancing your timing like it should as you add RPM.

 

[cellomaster]

As far as I can tell it looks fine. I put some oil on the pivot points, and springs, and everything moves very freely. They work correctly in tandem, and the cam moves as it should when they move.

 

[RobMan]

I know you said you followed the FSM but you said for timing you adjusted the backing plate which is correct for the left but for adjusting timing on the right side you have to slightly open or close the point gap of the right points to set timing on that side.

 

[cellomaster]

Just confirmed it, but both points break exactly on fire marks. Left side is .013" and right side is .016"

 

[RobMan]

What points are you using? Are they the ones that were in the bike when you got it or are they replacements and if so what brand?

 

[cellomaster]

What points are you using? Are they the ones that were in the bike when you got it or are they replacements and if so what brand?

No, not original. The old ones were seriously corroded, so I bought new ones off of 4into1.

 

[cellomaster]

I reset the points plate to be in the direct center of that little notch, then set each point to fire at its correct time. Took it out for a spin, and I've never felt so much power on this thing. It rips like it was made yesterday, wild acceleration, and I'm actually hitting the top end now. I don't know if this gives you guys any ideas as far as what's wrong with it, because I know this is not how you should time at according to the FSM. I feel like it definitely has something to do with the advancer. I checked the gaps, left side is .023, right side is .022. so certainly above where it should be, but maybe that's okay

I am sure I did a better job at setting the timing then I did the first time, so that may be why it feels so much more powerful now.

 

[ancientdad]

Glad it's running better, and I knew the gaps were wide the moment I saw them. The location you have the points plate in is the default position. If the F and LF marks show correctly, there's a mystery as to why. With gaps that wide and the plate in that position, the static timing should be fairly advanced of the F and LF marks, hence the reason the spec is .012" to .016" for that plate position. Something is going on, it could be the exhaust cam is one tooth retarded from a previous rebuild, who knows. But, have you checked the full advance timing with a strobe yet?

 

[cellomaster]

But, have you checked the full advance timing with a strobe yet?

No I haven't. Hoping to do that here soon, just haven't had the time to run out to the store to rent one. You run the timing light at 4-5K rpm, right?

Is there any danger to keeping the gaps wide? It will move the spring further, so would that wear out faster, if even noticeable? And the larger gap probably means larger spark, so it can ark off the cap, but that would be momentary, right?

 

[EzPete]

No I haven't. Hoping to do that here soon, just haven't had the time to run out to the store to rent one. You run the timing light at 4-5K rpm, right?

Is there any danger to keeping the gaps wide? It will move the spring further, so would that wear out faster, if even noticeable? And the larger gap probably means larger spark, so it can ark off the cap, but that would be momentary, right?

Points will wear faster, have some arcing possibly and you’d see some high rpm misfire and weak spark due to the lack of dwell time for the coil to charge.

Taking a look at the timing under strobe will tell a lot.

 

[cellomaster]

I am also rebuilding a 383 Stroker SBC on the side, so I'll find some time at some point soon to do that...more projects than time allows, what a wonderful problem!

 

[cellomaster]

I played around with it a little bit more today. I had to order a timing light, because my local auto parts stores don't rent them. And I was impatient today, wanted to ride it

This is what I ended up coming to. It still has some really good power, it's not doing the misfire / no spark anymore, it's very smooth and consistent rise and fall. Once the timing light comes in, I'll be sure to check it again.

 

[cellomaster]

Is just able to retime and confirm everything now that my timing light has come in. It is idling between 1,000 to 1100, and at idle is firing right on LF mark. I gapped both left and right points before doing the timing light, and started them both off at at .014". At 4000 RPM, the advance is firing in between both the advance lines. Is this all correct, should it now be running good, or did I do something wrong? I haven't yet taken it for a ride.




Just checked the gaps for both points, post timing light changes. Left side is 0.013, right side is 0.010. do I need to increase the gap on the right side?

 

[ancientdad]

Is just able to retime and confirm everything now that my timing light has come in. It is idling between 1,000 to 1100, and at idle is firing right on LF mark. I gapped both left and right points before doing the timing light, and started them both off at at .014". At 4000 RPM, the advance is firing in between both the advance lines. Is this all correct, should it now be running good, or did I do something wrong?

You mention that LF is properly timed at idle, but you didn't mention the F mark for the right side. You have to check both sides independently, manipulate the points plate to get the left side correct and then manipulate the points gap within the spec range to get the right cylinder correct at F.

Just checked the gaps for both points, post timing light changes. Left side is 0.013, right side is 0.010. do I need to increase the gap on the right side?

Obviously you want the timing right on both cylinders WITH the gaps in the spec range, but changing the right side gap will directly affect the timing and it will have to be re-checked. Again, it's a process back and forth between sides and it requires patience.

 

[cellomaster]

Ahhhh! Yes! Thank you! I totally forgot that the right side had to be confirmed, and edited based off the points Gap. I just redid it, for the right side, idle is now firing on F, and at 4000 RPM, it's firing within the marks. The points Gap for left side is still 0.013, and for the right side it's now 0.016. everything should be spot on now!

 

[ancientdad]

Ahhhh! Yes! Thank you! I totally forgot that the right side had to be confirmed, and edited based off the points Gap. I just redid it, for the right side, idle is now firing on F, and at 4000 RPM, it's firing within the marks. The points Gap for left side is still 0.013, and for the right side it's now 0.016. everything should be spot on now!

Close enough, and now you fully understand the process and are hereby VHT certified to do your future points and timing adjustments.

 

[cellomaster]

Well, it's still having the same issues I was explaining previously. It is still bogging down, then randomly just having an incredible burst of power and repeating the cycle. With plenty of back fire along the way, small and big pops. Does this point to a bad advancer?

 

[ancientdad]

Well, it's still having the same issues I was explaining previously. It is still bogging down, then randomly just having an incredible burst of power and repeating the cycle. With plenty of back fire along the way, small and big pops. Does this point to a bad advancer?

Midrange rpm? Can't recall, but have we checked and ruled out condenser or condenser ground?

 

[boddy]

Well, it's still having the same issues I was explaining previously. It is still bogging down, then randomly just having an incredible burst of power and repeating the cycle. With plenty of back fire along the way, small and big pops. Does this point to a bad advancer?

I would orient the points wire to be the same as the left side. I suspect the way the terminal sticks out it is grounding on the cover. Take it for a spin with the points cover off to confirm.

 

[cellomaster]

Midrange rpm? Can't recall, but have we checked and ruled out condenser or condenser ground?

I have not, no. I did replace all of them, they are brand new, but this is a possibility.

would orient the points wire to be the same as the left side. I suspect the way the terminal sticks out it is grounding on the cover. Take it for a spin with the points cover off to confirm.

Sounds good, will do. Stand by.

 

[ancientdad]

I have not, no. I did replace all of them, they are brand new, but this is a possibility.

All?? LOL, there are only 2 and they're mounted to the coil bracket if original or original replacement. But what about the coil bracket ground? This has been going on for a while and I can't recall if you've painted the frame or anything that would affect the ground for the condensers.