Rich, the bad way
 

well i finished my engine rebuild a few weeks ago (1988 domi) thanks to every one here. its been running well but im having trouble with it being too rich.

its got noisy race pipes, a KandN filter(cleaned and re oiled) and a chopped off snorkel thing.

at first it had a 160 main jet and 50 idle jet.
ive since got it down to 155 main and 45 idle.

i've played around with the adjustment screw and find that the idle speed keeps increasing as i turn it clockwise until i cant turn it any more.

i've cleaned out the carb a few times, checked float height, replaced the float valve and needle seat with good condition second hand ones.

i've also noticed some kind of smoke coming out of the air box which is a recent development since putting the 155 jet in.

the choke cable has been disconnected at the handlebar controls to ensure its not on, the threaded part at the carb end has been stripped but still screws in, would this somehow change the pressure some where affecting the choke? i've tried sealing it a bit with silicone.

could the richness be caused by the rebuild? i think i've heard that somewhere. It must have been running for years with a 160 main in so it seems mad that its rich even with a 155.

i've just ordered a new air filter as i read on my k and n cleaning/oiling kit that the fibers can tighten in some circumstances.

it doesn't run too badly but there's lots of soot round the exhaust outlets and on the spark plug.

today i found oil in the air box drain tube, it was red (same colour as the air filter oil). could it be that i over oiled the filter?

please let me know if anyone has any ideas about this, it would be much appreciated.

Try seeing how it runs with the oil filter removed

im guessing you mean air filter, will give that a go

der
 

Yes! sorry about that, I think I must have been thinking of the filter oil in the air box (if I was thinking at all!)

ah i think it must be over oiled after a bit of research.

i didn't think it could be the air filter before as i remember it suddenly started running rich before the rebuild during a bit of off roading. i thought i had maybe damaged the carb when a stick got lodged in there but i had probably just got the filter wet in big puddles.

now its just rich from too much oil... i hope

well, i thoroughly cleaned the oil from the air filter and it still ran rich.

then i tried opening the side cover for the airbox and it ran very lean,

then i put the cover back on and took the filter out and found the plug didn't look sooty but the exhaust outlets did.

any ideas what the smoke coming out the airbox is?

Are the breather(s) from the crankcases routed to the airbox, usually are these days to reduce pollution.

yeah, i've worked out the smoke is coming from the crankcase breather tube. why would that happen?
its been rebored, new piston and rings etc,
its not burning oil,
its not over filled with oil

also could the smoke from the breather be causing it to run rich as its filling the airbox and stopping fresh oxygen coming in?

Is it smoke or condensation? If it was me I think I'd run it in as is, keep it steady and get some miles on the engine. The way I used to check mixture was to get the engine good and hot then give it a good, throttle to the stop, thrashing along a long straightish, slightly up hill (very quiet!) lane, when flat out in top I'd pull the clutch and hit the kill switch, stopping with a dead engine then whip the plugs out (burning fingers) and adjust the carbs to what I found. Looking at the plugs when you haven't thrashed it doesn't really tell you much. Rolling roads have superceded this method

thanks for the help so far.

not really sure exactly what it is, it doesn't smell very nice though.

i took it for a long ride today and its still smoking/misting from the breather.

the iridium spark plug looks quite white at the tip of the insulator but the rest is black and sooty but not as bad as before, the exhaust outlets are also sooty but not as much as before

I think it's normal for some fumes to be escaping from the crankcase breather but if they're causing the filter to block or oil to accumilate in the airbox that's not good.
I did over 4,000miles in morocco on my Dommie 5 years ago with no problems; I ran a standard Honda air filter which if I recall was paper.
Before I left I tried restricting the air into the airbox by covering the front of the snorkel with some stretched material from a pair of tights...it ran awful !
It made me realise how sensitive it was to fueling changes.
If you're not familiar with using oiled air filters go back to paper.
The other option is to put the bike on a dyno. I recently took my xr400 to pdq, it cost me £70 for 2 runs and a change of main jet, it's perfect now.

The other cause may be the engine rebuild, was it done properly? you say you done it yourself so I guess only you can answer that q. if the valve timing is out or clearances are badly adjusted that could cause fueling problems.

theres no oil entering the airbox, just fumes.
i'm waiting for a standard filter in the post, will stick that in when i get it.

as for the rebuild being done properly, probably not spot on but near enough.

i did my valves again this morning, they seem to go out of spec pretty quickly.
i've been doing it by putting it at the TDC where there's some movement in the valves and setting them appropriately, is this correct? as i know its not quite as straight forward as it seems

also, yesterday it started making a racket from what seemed like the top end. it started suddenly and was in time with the revs. i stopped the engine straight away and the noise had gone when started again. i'm thinking it could be the decompressor as i had started it with the kick start which i very rarely use.

If you're happy with the rebuild then eliminate that concern. I'm assuming the valve timing is correct? check the marks on the cam drive gear

The clicking noise sounds like, as you say the de-compressor sticking.

As for the valve clearances going out of sync this should not happen. It sounds like you're setting the clearance , tightening the lock nut but not holding the bolt still with a screwdriver whilst nipping up the lock nut; it can slip around as you're tightening and change the gap. However, they would have to be so far out as to cause the problems you're experiencing.

When you set them are they at tdc on the compression stroke? Perhaps you have the engine at tdc on the exhaust stroke. As you turn the engine (remove the spark plug and use the kick start or rear wheel - make sure the engine is turning the correct way), watch the valves opening and closing... before you arrive at tdc on the compression stroke, the inlet valves should have just closed.

After you have set them turn the engine a few times and re-check.

If it still runs rough check the jets and needle and return to standard using the original air filter