gt380 rebuild conundrum: won't fire up, owner baffled

[Ramjam]

Dear members
I've just split the cases and replaced some crank seals and upon rebuilding have run into a snag. Bike just won't start despite aligning the ignition timing more or less perfectly with a gauge. I have clean sparks on all three but i'm wondering about 3 possible things which might prevent it running.

1) when i put the carbs back, i managed to break off an old breather tube, which i think runs from one of the bottom chambers of the carbs and, if i'm right, is supposed to go up? So when i put gas in it, it started pissing out the bottom. Could this be to do with the tube, or is it likely that the floats might be sticking?


2) I also primed the CCi tubes with old engine oil so i could check when the new, red 2 stroke oil travels through. I'm not sure this was wise though as i used old oil which was a bit black and when i take the plugs out to inspect them, i find that they they are wet and oily black. Could this effect their spark?

3) This time, before trying to start, i took the head off to gauge the BTDC and i noticed a tiry bit of water and oil on top of the piston dome. Anything significant? Could there be water in my gas?


As a footnote, the bike started for less than one second on the very first kick. I am inclined to believe that i have a fuel problem. Please help with any advice as it's doing my head in.

thank you

mj in Beirut


Only gt380 in Lebanon

[titan performance]

If the plugs become fouled on 2 strokes, they don't run properly, if at all.....so checking their condition is essential. Once fouled, plugs will sometimes never work again, no matter how much you clean them. I have experienced this with plugs that appear to be in perfect physical condition.
Using the incorrect oil, while not recommended, probably wont prevent the engine from at least firing.
If petrol is leaking from an overflow, then you have worn or sticky stop valves, stuck floats, or badly adjusted float heights.
If you think the petrol is suspect, drain your tank down thoroughly, and use some fresh petrol....water finding it's way into fuel station tanks is not unheard of over here in the UK, so possibly the same in other countries.
If it were me, I would fit new plugs, fresh petrol, check my carbs and use the correct oil.....and if it still doesn't run, the problem lies outside of these items.

[Ramjam]

thanks for that. Two questions. Is there a way of draining the petrol out of the carbs without removing them? And secondly, even if the floats were not stopping the gas, surely the engine would still run - or is it possible to flood it? Does that make it harder to start?

ok, that was three.

thanks

mj

[Vintageman]

It would have flooded it and you may have a lake worth of gas in your crankcase that had the carb leaking. Also that exhaust pipe may have a lot in it too

You brass float for that carb may have a hole in it and sinks not float.

You need to pull the carbs and see what's up.

I am not sure if GT380 has drain plugs for cases?

If so drain.

If not I have taken off tank, take out plugs and that pipe and put a rag over top (may still spray and ruin any new paint jobs) of and push engine in gear to blow out fuel. make sure key off no spark then gas fire. also go easy incase have a lot of gas and hydro locked. Don't want to bend a rod

[Cragdog]

thanks for that. Two questions. Is there a way of draining the petrol out of the carbs without removing them? And secondly, even if the floats were not stopping the gas, surely the engine would still run - or is it possible to flood it? Does that make it harder to start?

ok, that was three.

thanks

mj

I would flush out the crankcase, get rid of the old oil, prime the pump lines with good 2 stroke oil, new plugs.
The carbs can be drained by loosening the screw at the bottom of the float bowls, but it sounds like you need to remove them altogether to check your floats, I believe 25mm is the appropriate float height for your model. Make sure all your hoses are clamped securely and no vacuum leaks. Beach sync as best you can and try again. Hope you get it running Let us know how it goes.

[Alan H]

Can't remember what model 380 you have and my service manual is only for the J and K, but here are the details anyway.
If you PM me your email address I'll send all of it. It is nearly 4 megs though.
Looks like the J/K models are type 'A' and the measurement is 24.25mm. That is for the separate carbs (one cable to the twistgrip), not the manifold type where they are all linked together and have 2 cables going to the twistgrip.