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Discussion Starter · #1 ·
Hi all

So a quick summary

Recently bought a 1971 CL350

It has not really been run properly for approx 10 years.

I've stripped the carbs, cleaned everything, new o rings, checked diaphrams, basically given both carbs a thorough service.
Carbs have been synched both for idle and cable.

Replaced the rubber inlet manifolds and gaskets (also used some yamabond to be 100% sure)

Brand new genuine airfilters

Cam chain tensioner adjusted

Valve clearances checked

Ignition timing set

Tank cleaned

Fuel tap cleaned, new O ring.

New plugs

The bike will start and idle off the throttle at a nice steady 1200 rpm, however 50% of the time if the bike is revved to anything above 3000 rpm it hangs at this speed. I am thinking its the slides that are sticking, will giving them another good clean and perhaps slightly stretching the springs resolve this?

Another issue is I'm getting a bit of smoke from the cam cover breather, I noticed when i removed the exhausts that there was a lot of soot in the exhaust ports. Is there a chance that this will clear up with use, or is it likely that its a worn valve or similatr issue.

I'm not new to old bikes but only ever worked on vintage Yamaha 2 strokes in the past so the 4 stroke top end is a bit of a mystery to me at the moment.

Hope I haven't ramlbed on for too long.

Cheers

Tim
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Discussion Starter · #2 ·
Ok so I'm impatient, been scouring the forum and internet and it seems that this hanging of the engine speed is a really common problem, but, nobody seems to
finish a thread with how they fixed it.
I'm ready for stripping the carbs again but have read that it could be related to the timing advance mechanism.
Has anyone succesfully addressed this problem and how did you do it.
Thanks in advance (pardon the pun)
 

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Discussion Starter · #3 ·
Well got no idea if this is for real but i've just pulled the points and greased the timing advance mechanism, the springs looked a little dry, and it seems to have worked.
I used the CMC method when i set the ignition timing so put the points holder plate back by eye so the slots lined up, i suppose i will have to recheck that the timing is still spot on.
Anyway the 3000 rpm hang has gone and it comes back down to a 1200rpm idle (the last 500 rpm drop is a little slow but i can live with that).
Next job is to get the clutch adjusted then take her for an inaugral ride (away for a week so will have to wait)
Also the cam cover breather smoking has calmed down a lot so perhaps lack of running was the problem there.
Will update if anything changes.
 

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Another possible cause of slow return to idle could be vacuum leaks between the carbs and the head.
 

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Discussion Starter · #5 ·
Ive installed new genuine carb rubbers and gaskets and also se some yamabond to be sure everything is leak free. I did spray some wd40 on them when running and it made no difference.
 

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Great looking bike the Tim.

I've also had problems with the engine hanging between 2 and 3k. New throttle cable, boots among many other things and multiple engine teardowns. I've read somewhere that a tight valve clearance can also cause this. I've just learned to live with mine, I'm just a smidge looser than what the manual calls out for valve tappet clearance, but when I loosened the clearance enough to nearly get rid of the throttle hanging, the valve tappets got significantly louder.

Sent from my VS425PP using Tapatalk
 

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Discussion Starter · #7 · (Edited)
Thanks for the reply - i seem to have got rid of the problem by lubricating the advance mechanism behind the points. Its running really well now.
The bike has been virtually unused for many years so I wonder if just running it has made things better, but the only thing i did was lubricate the advance mech and the
hanging has vanished.

The bike looks nice from 10 yards away but it needs a lot of cosmetic work. Its complete and all original apart from having a CB350 side cover.
Still got a 1974 New York Licence sticker and the New York dealership sticker on the rear mudguard.

I cant decide whether to leave it alone or do a full restoration, those horrible rectangular mirrors have already been taken off !
 

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It would definitely be worth at least going thru the top end once the cold weather comes back. It's a bit frightening at first but there are so many resources online and the guys at common motor collective are a huge help. Depending on how long it has been sitting and how much money you wanna through at it, you could remove the top end, get a good look at the the cylinder walls to see if they've rusted at all and decide where to go from there.

My 360 was completely torn apart when I got it, and the last time it was plated was 86' or so. I gave it a good honing, new rings and religiously followed the service manual and she has treated me well this season after about 1000 miles. Been a great bike to learn on and pretty reliable as long as you keep up with the short service intervals.

Sent from my VS425PP using Tapatalk
 
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