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2746 Views 55 Replies 7 Participants Last post by  Bigjohnson20
I have a trailboss 325 and in neutral and reverse it revs up like it should, but once I put it in drive it only goes like 20 mph. I put a new primary clutch on it and I put new buttons in the secondary. Don’t know the problem.
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Reading reply #16 makes me think it could be fuel/air problem even more.
The valves were bad with the old top end in it. I have never checked the fuel, but it does run lean because the spark plug has a white tip. I tried adjusting the needle but it won’t do anything. Should I order a new fuel pump?
I think it is getting enough fuel though because I can rev it for as long as I want to in neutral.
What I will do is I will go to a oem polaris dealer and order the main just idle jet and a couple bigger sizes and a new needle to see if that does anything.
You said the compression is 90PSI, did you look up specs? Is that within range? It sounds low to me, but I’m not an expert on your machine/engine.
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I think it is supposed to be around that range, but never looked at specs
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I don’t wanna put much more money into it, but I want it fixed. Do you guys think I should try a bigger jet?
90 psi seems low to me as well but i do not have the manual to look in, generally i like to see 120 ish of compression
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I am thinking of pulling the motor out of the quad to be able to work on it clean and check out the bottom end. I did everything with the motor in the quad and I could of messed up somewhere I guess.
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I will let you guys know how it does after I pull the motor to check everything.
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B4 you pull... try doing compression test again but add a bit of oil to coat the rings and see if you get better compression.
I THINK your looking for 110-120 range.
I did that but I couldn’t get a test because oil was squirting out
also check the rubber diaphragm on top of carb for cracks.

"oil was squirting out"
from where? did you add to much? only need like a cap full.

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When you check diaphragm make sure it looks like top carb in this pic.
This picture is for reference its a 660 raptor that had similar problem
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Ok ya I added too much then. Makes sense. And ya I got a new diaphragm.
Did new diaphragm come with new jet needle? have you tried adjusting the clip on jet needle? #2 and #3 in Diagram.
another test you can try is remove exhaust.
Ya I have done all of that
Try redoing the wet compression test. You need that wet dry comparison to move on in troubleshooting. Do you know the history of the atv? like what happened to the valves?
I do not know. What I know is that my uncle bought the ATV and right when they unloaded it it blew up or something. He never messed with it and it sat for probably 6 years and I bought it off of him.
6 years! Could be electrical. Do the compression comparison test. if passible post up a video of the problem. A video helps a lot!! and can get some attention from the most experience members
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