CB350 1971 Restoration Project

[BenPowell]

Clutch action does not sound right, clutches can stick when left unused for several months but not every time.

Might be your clutch cable is sticking.

It’s a strange one, I assumed it was because it had been stood for a long while, but I took the side cover off the engine and you can see the clutch disengaging, but the individual plates stick, it’s like how two really flat surfaces put together will grab.

It may improve once it’s had some heat through it and been bedded back in. Can only try I suppose

[BenPowell]

I'm at the carb tuning stage with my 350 Ben (next week as going away till next week) - tuning seems basic. Have a look at page 60 in the workshop manual (in Ash's dropbox)
My clutch was dragging a bit too but not test rode it yet - have adjusted most of the drag using the screw and nut adjustment.
I think Ash may be the man to ask!

Let me know how you get on with yours when you get round to it, I read the book and agree it sounds straight forward. My carbs were in a bit of a state when before I cleaned them up so could be something else, just don’t know what.

[philward]

I'm at the carb tuning stage with my 350 Ben (next week as going away till next week) - tuning seems basic. Have a look at page 60 in the workshop manual (in Ash's dropbox)
My clutch was dragging a bit too but not test rode it yet - have adjusted most of the drag using the screw and nut adjustment.
I think Ash may be the man to ask!

Let me know how you get on with yours when you get round to it, I read the book and agree it sounds straight forward. My carbs were in a bit of a state when before I cleaned them up so could be something else, just don’t know what.

Will do Ben

[BenPowell]

Bit of a follow up from my last few posts.

Clutch drag - after running the engine for a while and getting some heat into the oil seems to have solved the issue, still feels like it has a fair bit of drag when the oil is cold compared to being hot, but seems to work okay. I think it will probably improve further once it’s had some use.

Carbs - my float height was incorrect causing a really rich mixture, for the 3D carbs the float height needs to be 26mm, I initially set this at 21mm as per some manual but obviously it differs depending which carbs are fitted, I was able to get the bike idling nicely and had it moving under it’s own power for the first time, which felt like a bit of an achievement. I still think the carbs need some more work the left cylinder seems to run fine, but the right seems to pop/backfire down the exhaust when letting off the throttle, I think it is probably running a bit lean based on the spark plug colour. Will need to check for vacuum leaks.

I rechecked points and valve clearances tonight, checked the auto advance functions freely. Will probably get the carbs off Wednesday for another clean I suspect the idle passage is blocked slightly.

Will report back if popping and banging from right side eventually stops,

V5 Application - got a letter in the post today from the DVLA, turned out to be a request for a vehicle inspection, just my look. Anyway they’re coming in Friday to look at the bike, hopefully shouldn’t be much longer till I get the V5.

[McCabe-Thiele (Ted)]

Always good to read  about updates.

[philward]

Had a go at settings on mine yesterday too Ben. Running awful really. Similar issues to yours. Balanced the carbs but slow to return to idle. Got good compression at 160 on both cylinders. Going to recheck all settings, check for inlet leaks.
I'll report back too if any progress

Sent from my moto g(50) using Tapatalk

[BenPowell]

Had a go at settings on mine yesterday too Ben. Running awful really. Similar issues to yours. Balanced the carbs but slow to return to idle. Got good compression at 160 on both cylinders. Going to recheck all settings, check for inlet leaks.
I'll report back too if any progress

Sent from my moto g(50) using Tapatalk

Mine sometimes hangs at around 3/4K rpm. Only occasionally though, most times it returns to idle quickly, but a quick blip of the throttle returns it back to idle, sticking slide maybe?

Frustrating thing is I would have liked to work on the carbs this week but with the inspection on Friday it’s probably best to leave the bike fairly complete. I’ll have most of the weekend to work on them and try making changes, I will try to make one or two changes at a time to narrow down the issue.
I will investigate for air leaks probably Wednesday/Thursday since I can do that with the bike together. And also run it to see if the timing/valve adjustment has had any effect.

Bu yeah please keep updating, no doubt we won’t be the first or last to have these issues, on other forums posts aren’t followed up with results so become a bit difficult to pin point potential problem areas.

[AshimotoK0]

Had a go at settings on mine yesterday too Ben. Running awful really. Similar issues to yours. Balanced the carbs but slow to return to idle. Got good compression at 160 on both cylinders. Going to recheck all settings, check for inlet leaks.
I'll report back too if any progress

Sent from my moto g(50) using Tapatalk

Mine sometimes hangs at around 3/4K rpm. Only occasionally though, most times it returns to idle quickly, but a quick blip of the throttle returns it back to idle, sticking slide maybe?

Frustrating thing is I would have liked to work on the carbs this week but with the inspection on Friday it’s probably best to leave the bike fairly complete. I’ll have most of the weekend to work on them and try making changes, I will try to make one or two changes at a time to narrow down the issue.
I will investigate for air leaks probably Wednesday/Thursday since I can do that with the bike together. And also run it to see if the timing/valve adjustment has had any effect.

Bu yeah please keep updating, no doubt we won’t be the first or last to have these issues, on other forums posts aren’t followed up with results so become a bit difficult to pin point potential problem areas.

Don't think they will be bothered about carbs being off Ben. More a visit to check validity of numbers on frame & engine.
Can always loan you some 350 carbs to try to identify the problem

[Bryanj]

Carb diaphragms maybe, was one on here a while ago with that problem, ds does pattern ones when in stock but aint cheap

[Oddjob]

Any of say the earlier versions that don't use CV carbs, maybe swap them for Non CV carbs?

[florence]

My 350 always had problems with sticking slides, I've owned and ridden one for 40 years and they were always trouble, especially in wet weather. Sometimes they were happy and other times they were a pain.  In my opinion the carbs on these are not a great design so I changed mine to slide carbs (Amal concentrics in my case), i.e. non diaphragm, and it transformed the bike.  I know that is no good if you are after authenticity but in all honesty it is a vast improvement.  It runs brilliantly and throttle response is instant.  I would say it would depend on how much you want to ride the bike.

[AshimotoK0]

Carb diaphragms maybe, was one on here a while ago with that problem, ds does pattern ones when in stock but aint cheap

His diaphragms are perfect Ken. 1st thing we checked when he took his carbs apart\

[AshimotoK0]

My 350 always had problems with sticking slides, I've owned and ridden one for 40 years and they were always trouble, especially in wet weather. Sometimes they were happy and other times they were a pain.  In my opinion the carbs on these are not a great design so I changed mine to slide carbs (Amal concentrics in my case), i.e. non diaphragm, and it transformed the bike.  I know that is no good if you are after authenticity but in all honesty it is a vast improvement.  It runs brilliantly and throttle response is instant.  I would say it would depend on how much you want to ride the bike.

I have a pair of 750 cabs that have been modified to fit the CB350 but never tried them. They were off a CB350K4 racer. Also the early SL350 had Keihin slide carbs.

[Oddjob]

Carb diaphragms maybe, was one on here a while ago with that problem, ds does pattern ones when in stock but aint cheap

His diaphragms are perfect Ken. 1st thing we checked when he took his carbs apart\

But for how long Ash, never liked them myself. Always seem to hole for no reason..

[AshimotoK0]

Carb diaphragms maybe, was one on here a while ago with that problem, ds does pattern ones when in stock but aint cheap

His diaphragms are perfect Ken. 1st thing we checked when he took his carbs apart\

But for how long Ash, never liked them myself. Always seem to hole for no reason..

Yea agree that the carbs are crap on that model but when last checked diaphragms were fine ... more likely a blockage somewhere.