SOHC.co.uk Forums > CB350/400
Smokey rebuilt 350
royhall:
Just dug out of my ever growing stash of bits, four used CB350F carb bodies that look in good nick. After I check the float levels later today I think I will give Matt Harper a ring see what we can do.
K2-K6:
Have you tried running it without the air filter Roy? And are you confident there is no impairment to the filter box entry?
Years ago I had a look at a bike that was doing something similar and the air filter, which had just been put in new, was not flowing properly. Never did figure out why it wouldn't flow air at the right volume. It defied logic and was replaced without any further issues.
It doesn't deal with the odd carb on no3 though.
royhall:
Checked that early on. As it takes its air from under the seat, I thought the plastic seat base on the repro seat may be bending down and blocking the vent, it wasn't. Will run it without the filter though, didn't think of that. The air filter has been common all though so who knows. Will let you know. Wouldn't that be tough to live down. ;D
royhall:
Just checked with the air filter out and the seat up and it is just the same. At least that's another link eliminated. The air filter smells quite strongly of petrol though, again indicating rich running. Just asked the question about the emissions readings and they are for CO.
Checked the float heights with the clear tube method. Pot 1- Can't check (flooding), Pot 2 - On the bowl crease (good), Pot 3 - Top of the screw threads (nearly overflow), Pot 4 - Bowl crease (good). I think Pot 1 is flooding due to it being way too high, and the extra ventilation is allowing it to flood. Stopped doing it when I removed the tube. A mixed bag really, all plugs are black with Pot 4 (the worst one) wet with petrol. Strange how the height on the worst one is correct? Carbs out again time. Matt Harper has offered to ultrasonic them again and check for cracks and corrosion etc. Gerben has sent me some Viton seals and stainless clips. I am also sending my 4 spare carb bodies so he can pick the best of the bunch. I don't think Matt likes to be beaten by carbs, appears to relish the challenge. Well I wish him the best of luck.
Off the road again for now until Matt waves his magic wand. One day you never know!!
royhall:
Well here we are 3 months later and bike still smoking badly on pot 4. The carbs went back to Matt Harper for another go as the float valves were a bit leaky. All that's sorted now and pot 4 is no different. I have also tried a set of carbs lent to me by a kind gentleman off a bike that is known to run okay. Same result so that's the carbs ruled out. Just ran it to hot in the garage and the plug from 4 has come out black and oily. Not sure where to go from here, so will re-cap what I have tried.
1. The engine ran fine after the 1st rebuild for 200 miles.
2. At this point cylinder 4 started smoking and it got so bad it wouldn't really run as it was filling the street with smoke.
3. Stripped down the top end as I was suspecting it had been bored to the wrong tolerance.
4. Had the bores re-done to 8 tenths of a thou (although they were okay the first time) that eliminated pistons and rings.
5. Re-did the valve guides that were reamed to new tolerance and the valves checked for wear.
6. Reassembled the engine using all genuine Honda gaskets and seals.
7. Carbs rebuilt again due to leaky float valves, another set of carbs tried. That eliminates the carbs.
Certainly looks like the top end is coming apart yet again unless someone can make a suggestion for something I have overlooked. This time I'm going to have to look for cracks/distortion/holes etc as that oil is getting in somewhere. Any ideas before I get a can of petrol and burn the wretched thing down to the ground. ;D
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