Missing carb screw, what next!?

[x-jetter]

well i took off my flame arrestors today to find that my throttle plate is missing a screw :banghead: i know it was there before so there's only one place it could've gone. i took off the intake to see if it got caught up in the reeds, but there's nothing there. compression is still good, and it ran awesome yesterday, so i don't know what to do. is there anything else i can do short of tearing the whole f***ing thing down?

 

[robertg]

I would tear it apart just to make sure. It would be a miracle if it went through the motor and out the exhaust without damaging anything.

 

[SUPERJET-113]

That sucks! Dont take the chance man, tear it down or you might regret it bigtime!
It may just be hung up somewhere waiting to unleash.

 

[Mile9c1]

That's a tough one... on one hand it seems to be running well long after the screw fell into the engine... on the other hand, if it's still in there it could cause major damage.

I'd pull the engine and look around inside the intakes, you'll be able to see it or hear it.

 

[x-jetter]

well the results are in, and major damage it is....

 

[x-jetter]

i still haven't found the screw either. i can't see it in the cases, but i haven't taken them apart (and reaaaaally don't want to) if it messed up the top of the piston like that it probably just went out the exhaust right?

also, how do i know if it's too bad for just a hone? it's already at 83mm so i don't really want to go any further, and if i just hone it i only have to buy one piston.

 

[Mile9c1]

You measured the compression, right? If it's good, just give it a light hone. You only have 1 overbore left.

The screw might be in your waterbox, take it out and check.

 

[x-jetter]

well the compression wasn't great, it was 180. this motor should be running about 190-195, but part of the piston is missing so that probably makes up for the difference. i don't know the first thing about honing nor do i have the equipment to do it so i'm just gonna drop by a local mechanic shop and see if they'll run a hone through it for me, and also get their opinion on whether or not it needs an overbore.

i turned the cases upside down and shook em around and stuff and didn't see or hear anything, so i don't think it's in there. i'll look in the waterbox tomorrow though. if it's not in there, does it pretty much have to be in the cases or can it actually go right through the waterbox too?

 

[Mile9c1]

It's like a 3mm long screw, it could be hiding anywhere!

 

[keefer]

It is hard to see the fuzzy piston pics, but I don't think that damage was from the loose screw. Looks more like water injestion or cold seizure. I would suggest tearing it all the way down if you don't find it in the waterbox. Also you should peen the carb shaft screws so they won't back out again. Have someone clean the aluminum from the bore and hone it. Have them measure the bores and determine if you can get by with 83mm pistons again. If you are running 195 lbs compression then you better mix in some race gas to avoid deto and more damage. Just my .02 worth :banghead:

 

[x-jetter]

i'm pretty sure it is from the screw. if you look at the top of the pistons, there are all kind of scratches like the screw was up there for a while, and the dome has a bunch of scratches and dents too. how do you 'peen' something? i have been running 110 mixed with 93, so i don't think that's a problem. i'm running wisecos right now, and i know they need a pretty precise clearance, so should i go to pro-x after this hone or will wisecos still be alright?

 

[Matt_E]

I think Wiseco's need more clearance than Pro-X - but I could be wrong.
That sucks, I just had a very similar thing happen to me. Except it took out a sleeve AND a piston in the process.

 

[x-jetter]

well i just got back from the shop here and he honed it for me and ordered a new piston and new rings for the old piston, so i'll be ready to ride again this weekend. :biggthumpup: he said the clearance (before hone) was 7 thousands, so that's not good, but i should be good for the rest of the year at least. the scratches and holes from the screw have carbon deposits on them already, so it looks like this happened a while ago. it looks like this is why it's been so hard to tune this thing all year. :arms:

since i'm putting in one new piston and two new sets of rings, does this mean i have to do the break in procedure all over again?

 

[Matt_E]

I would think yes.

 

[x-jetter]

oh boy, i figured this would be a good time to rebuild the carbs, and what do you know: two dissimilar carbs. one is a very old model while one is pretty new. that's just great. i'm gonna pop them on there and try to dial them in, and if it doesn't work i'm taking one of them to Keith Head to have him 'big dawg' it and be done with my tuning nightmares.

oh and to top it off, neither carb had a filter in the fuel pump :banghead:

 

[Matt_E]

If they are truly different versions, don't bother trying to tune them as duals.

 

[x-jetter]

they're definately truly different. one uses orings in the fuel pump and the other uses the square gaskets. other than that they look identical. serial numbers are 61x01 and SH 34

they seemed to be doing pretty good before, so i think i'm gonna try them just because i don't want to spend more money unless i absolutely have to.

 

[Matt_E]

They more than likely have different internal fuel circuitry - something you wouldn't be able to tell looking at the parts.
Seriously, you would be better off not wasting any more time on them. Get a matched set.

BTW, the gasket vs. O-ring is, I believe, only an issue of older 44 vs newer 44. But, the serial numbers are different.

 

[Mile9c1]

Are you looking at the serial numbers under the fuel pump covers? The 61X is off a 61X for sure, I've never seen an SH 34 that I can remember.

 

[x-jetter]

like if you look at the fuel pump straight on, it's below them. or do you mean if you take off the fuel pump and look literally underneath it?