Runs very poor on low end - will not stay running or rev up nicely - have to work it up as it bogs bad, warm or cold - runs fine at and just before clutch engage point and up

Ok so here is what I have done :

cleaned carbs - completely - replaced main jets 350's
checked compression 100 PSI each
drained fuel and added fresh
unplugged and replugged all connectors
checked spark - good

So I got it running and ran it a bit while blurping the throttle hoping it would free up but didn't - though maybe a bit of the old bad gas still in lines so purged them and the primer as well and drained float bowls

So my options

1. re clean and check carbs - maybe there was some crap stilling in fuel tank it sucked in - in that case remove and flush tank good
2. check that the power valves are nto stuck open
3. check the reeds for chips
4. check again for air leak in boots and gaskest but look fine and not over or under tightened
5. tried adjusting idle - no change other than it stay running if you crank it way up but shouldn't have to


ANYONE - else have and ideas to check

I was also wondering which plug wire goes to which cylinder - seem to run the same no matter which is on which one - got it with wires off - assume left lead from coil goes to left cyclinder but have seen them different before - also can't think of why it runs both ways? Pick up must sense spark timing and not matte rwhich is on which on?

Someone want to educate me that would be sweet.

Ok as far as the spark and which wire to which cylinder - figured that out.

It actually doesn't matter - since it sparks at both BTD and TDC. Why? Maybe to burn any unburnt fuel but can't really say exactly why they would need to do that. Actual reasoning would be nice if anyone had some just to get a little education, always looking to learn, that's why if like to fix stuff.

Now on to the rest - any tips would be great but I am sure I'll figure it out with a little tinkering.

Starting with idea one and working my way down!

100psi???

ouch rotary valve Rotax are in the 135-145 range

my STX 583 was 140psi with 17,098km no rebuilds



no reeds on a RV engine

engage at 3500 or so top rpm 7800

Fuel pump diaphram ripped? or dirty?

Thanks for the replay man - yea looked at it again - definetly no reeds, my bad!

So took back off the carbs, despite me having cleaned them once. The issue was the threads on the low speed were still full of stuff you couldn't see, enough so when I ran the jets back in it was pulgging the end, ran them in and out may times and got them cleaned. Check everything else again and reset to roughly stock settings.

Reassembled and fired right up

So sound like the compression is down a bit, I'll run it some then check again - hasn't been used in like 3 years so maybe the rings are slightly sticking and not seating. If he want to foot the $$$ I will gladly throwin a new topend. I know it has been poorly maintained, they never fogged it and the air box was not even screwed down when I got it, just floating aroung in there mostly off the carbs. The crab were plugged with green jell from the bad gas.

Thanks!

read your other post on jetting

I gave you the updated specs for the STX

the jets are staggered

Thanks man, everything I needs and more!

Should have a 330 on the mag and 320 on pto. 100psi is too low, i'd throw in some new rings.