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compression testing


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ive been struggling to get my shee jetted right. its been super hot lately here but nothing seems to help the breakup on the top end. i just bought a compression tester but what was wondering what would be decent to good compression. it starts up 2nd or 3rd kick and runs good midrange just as soon as its 3/4 to full it has hesitation. heres my mods

trinity stage 4 head(not sure on dome cc)

fmf gold series into turbine core

dual foam filters no box

v force 2 reeds

330 main

air 1.5 turns out

needle is 4th pos. (1 up from botttom)

temp has been well over a 100 lately .

 i just dont want to have to take it to a shop to get checked out

 

 

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no leakdown test done yet i dont have the tools to do it and not 100% sure on how to do it. running 91 with octane booster at 3300 feet. i originally bought it from someone who rode it in flagstaff az which is around 6000 feet and alot cooler. guy didnt know much about bike since he got it on a trade and only rode it a few times. siad he preferred 4 stokes

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More info needed: your elevation and PO's relative temps.

 

I'll bet a Buck you're pushing to much compression. If it were me I wouldn't even ride it to do a plug chop until you get it sorted out better.

 

Do a comp and leakdown, then pull a dome and check size. If they are Trinity domes you might not want to use them no matter what, just ask Windy.

 

JMHO, your results may, and will vary.

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Glad to hear I have a couple of followers. LOL

 

TRINITY = 2 stroke V.D. (your going to want to see a professional to get that treated.)

Your going to need to do a compression check as well as a squish measurement. Because there is no reason that bike should have needed 380 mains previously. With your current jetting it might be as easy as dropping those needles to adjust for the heat........but since we have "Trinity" in the conversation, then we need to assume your already in DETONATION LAND. So while it's that hot out, you might as well spend your down time learning a little more about your topend set-up before shit gets real and you end up having to learn about rebuilding an entire top end.

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i rode it before i bought it up and down the street and around a lil bit it ran good. i was on blacktop so i never eld it wot since it was ready to pull wheelies and i wasnt trying to upset the seller. ill look into a leakdown test since not 100 % sure on how to do it. like i said it runs good ive ridden it around for 30 to 45 min and the temp gauge says 180 even with it being 100+ outside. i dont know if thats good but thats where it stays the whole time riding. only when im giving it 3/4 to wot. i was also wondering if maybey it wasnt getting enough gas from the petcock. are most fuel lines ran over the boost bottle and not under

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false.....you can have a leak at your reeds, or base gaskets and it wont show on a compression test.  All the compression test is going to do is indicate whether both cylinders are healthy in relation to each other and to HELP aid in choosing an octane rating for fuel.

 

NOW....a leakdown test is totally different in terms of a healthy bike.  As 2strokes need fuel mixed with oil to lubricate......air causes extra internal temps which do all sorts of odd things to motors from melting pistons, to punching a connecting rod out the bottom. 

 

You cant tell by riding it if it has an air leak and is being compensated for with huge jets.  I mean shit......I run a dune/play port, vf2 reeds, k&n pods, 20cc domes, and fmf fatties, and I am running fresh 93 and am running 330 main jets at 80* and 1100'

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For one thing dump the boost bottle, it does nothing but crack carb boots, where you may be leaking air. Either get a stock crossover tube or get some pvc caps to fit the holes. That's what I did, installed with Yamabond and clamps.

 

Not knowing what your domes are could be the problem. If you wanted to play it safe put a stock head on until you sort it out. Make sure there are no pits in it and that it's flat and clean.

 

Search the forum on how to build a leak tester.

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