Topic: 350f driving me nuts

[Jay B]

OK, I'm appealing to the collective wisdom of the group. My 350f project bike has white smoke coming out of the exhaust, and I can't figgure out why. Here's what I've done so far- Tore down the top end and put in new piston rings, gaskets and valve stem seals. It had stuck rings in 2 jugs when I got it. Compression is 150 psi +/- a couple pounds on all 4 cylinders. New points and condensers and lubed the flyweights. I just marked the timing plate and reassembled, haven't checked the timing yet. Tore down the carbs and cleaned everything very well. Reasembled using new carb kits, jets are stock sizes. I'm running the stock air box, filter looks to be brand new. Pilot screws are about 2-2 1/2 turns out. Choke plates are opening fully. Plugs are new. I've put only about 40 miles on it since I got it running. It starts and runs great, except for the white smoke. When I pull the plugs, they are wet looking. I was really carefull with the float settings. I thought maybe they were too high, so I've shut the gas off to see if the smoke would quit as the fuel level goes down, but it continues till the motor dies. I'm not talking about billowing white clouds of smoke here, but enough to be noticable. Any tips comments or suggestions would sure be welcome, as this thing is really starting to drive me crazy.

[heffay]

put more miles on it... i'd be willing to bet that's all it needs

[Jay B]

put more miles on it... it be willing to bet that's all it needs

You're probably right. The miles will come when the weather straightens out. BTW, I got my seat cut down the other day, I'll make a cover for it soon. It's similar to yours, but with a more vertical face on the front side of the hump. Got some drag bars on the way, I should finish this thing up pretty soon.

[bwaller]

What kind of oil are you using? I decided to try synthetic after I restored my K3 a few years back. Engine wise the pistons were aok but deglazed the sleeves and installed new rings among other things. Long story short the synthetic oil had a negative effect on the rings seating, and although it ran like a top, it smoked some and inhaled oil! I tore it down again, barely passed the hone once more, used the same rings and went back to Castrol 10W-40. I did however try a trick I read about where you just use a touch of oil on the skirts, but leave the rings dry when installing the cylinders, and on start up run the engine at half redline for 30 seconds to do a quick break-in which I decided to try this time. It worked to seat the rings, the oil stays clean and uses none BUT I'm sure there will be those who won't agree with the technique. I believe our oils are tremendously better than when these bikes were new and even regular oils may have an affect on seating rings, so I agree with Heffay, ride it a couple thousand miles before you draw any conclusions. I hope your luck is better than mine that time around.

[oldbiker]

Exhaust smoke is usually dark to black if due to oil burning. White smoke is water vapour from condensation and ought to clear up when the motor reaches full working temperature.
How long does your smoking show itself?

[Jay B]

The longest ride I've taken is about 8 miles, it's been cold here. Still shows after that. I guess I would think that condensation would come from the breather tube rather than exhaust. I'm going to give it at least afew hundred miles for things to get familiar with one another. The smoke looks/smells like it's running way rich but it seems to run too well for that. Oh- I'm running 15-40 diesel oil right now. Its all I had and I've always heard its the next best thing to motorcycle specific oil.

[Tim2005]

Dunno about diesel oil, hmmm, but in any event I'd just check the timing then take it out for at least a 20 mile ride to settle it down. 8 miles at running-in speeds in cold weather may not be enough to get the condensation to clear from the exhausts.

[Jay B]

Dunno about diesel oil, hmmm, .

Yup, Diesel oil. There's nothing magic about it, it's just darned good oil. The stuff I keep around exceeds CH-4 ratings, which is a lot higher rating than the SJ car oils, and doesn't have the "fuel saving" additives in it that are death on wet motorcycle clucthes like the SJ has. Maybe motorcycle specific oils are better, I don't know, but this stuff beats the heck out of car oils.

[Finbar20]

You say the the plugs look wet, do they smell like fuel? If you suspect its running a bit rich I would try putting the original hardware back into the carbs. I've heard opinions both good and bad on aftermarket carb kits. Disregard this post if its new Honda stuff!

[bwaller]

Your 15W-40 oil is probably too high a viscosity if it's cold like you say. If you've just done the top end you might want to change oil anyway after an initial break-in, if you're able to continue to ride. (I sure can't in our weather!) Then consider a "thinner" oil, it's cheap insurance anyway.

[HondaMan]

The air screws are too far out. They should be no more than 1-1/2 turns, more like 1 turn out. That's why your plugs are wet and you are seeing smoke.
If the engine won't idle at 1 turn out, the float level is wrong, or the air emulsifier tubes are blocked (common on CB350F that sat too long).
The CB350F would idle for 8 hours straight, right out of the box. It had the best carb setup of all the SOHC fours. It would start at the instant the starter button was pressed, like it was an electric motor.

[Jay B]

You nailed it HondaMan. I had been reading the carb FAQ's and must have gotten specs confused with another model. I had been fiddling with the screws in that 2 to 2-1/2 turn range. I just went out to my shop and readjusted them to 1 turn out and it was much better. Now I need more miles to  get it run in. I'd agree- the 350f seems to have very good carburation, even misadjusted it started instantly and idled/ran great.

[dusterdude]

hondaman comes thru again.....who is that masked man?