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Discussion Starter #1
hello I recently perches'ed a 1999 honda fourtrax 300 4X4 and it was burning oil so I got a gasket kit and took the engine apart removed the old gaskets and seals and installed the new ones then put it back together and adjusted the timing then I went to start it and I had to give it a bit of throttle for it to start and the it would run really rough. Why? It allways ran vary well and smooth.
 

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So you've replaced valve stem seals and head gasket?

Is the timing correct?
Are the valve clearances correct?
Have you cleaned the carb as a matter of course after taking your motor apart?
 
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Discussion Starter #4
I bib not clean the carb after I had the motor apart. The timing I think is correct. I bib not check the valve clearances. The piston rings looked good.
 

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I think you are off track , first thing was to take a compression test , clean the carb , tank , petcock and get fresh fuel in it , adjust the valves all before disassembling the engine , and you can't judge the condition of a piston , rings or jug by looking at it ------------
 

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Here's the route I'd go next...

Set valve clearances, perform compression test (with throttle wide open), then thoroughly clean the carb. IIRC the compression should be somewhere between 170 & 201psi.

Even if you comp test comes back a little lower, let's say 160 for arguments sake, it should still run relatively smooth.
 

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most old Honda's are 0.006.
 

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Discussion Starter #12
Well I was right the timing was off so I got it right and it still ran a little rough so I cleaned the carb and now it runs great. Compression cold is 180 psi and hot is 170 psi thanks for your help
 

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Well I was right the timing was off so I got it right and it still ran a little rough so I cleaned the carb and now it runs great. Compression cold is 180 psi and hot is 170 psi thanks for your help
Good work Tractorboy, compression is steering towards the low side but if your not a hard rider it should see you another season before you want a top end build.

Since you've had it apart doing gaskets etc now would probably be a good time to do an oil and filter change too, maybe throw a new spark plug in at the same time ;-)
 

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Well I was right the timing was off so I got it right and it still ran a little rough so I cleaned the carb and now it runs great. Compression cold is 180 psi and hot is 170 psi thanks for your help
Good work Tractorboy, compression is steering towards the low side but if your not a hard rider it should see you another season before you want a top end build.

Since you've had it apart doing gaskets etc now would probably be a good time to do an oil and filter change too, maybe throw a new spark plug in at the same time ;-)
180 psi is low ?....ummmm..maybe I missed the short little yellow bus again ?, but I know for a fact !!, the trx300's ( most ), have a min of 100 psi to just run, and your saying 180 psi is low ?..hmmmmm..lol.
 

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good deal OP !!.
 

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170 is his warm reading, 180 cold so Yeah.. it's on the lower side of the FSM spec. 176 to 201 i think it is.. it may run at 100 but it's not right, there underpowered as it is, I dread to imagine what 100psi compression is like!
 

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170 is his warm reading, 180 cold so Yeah.. it's on the lower side of the FSM spec. 176 to 201 i think it is.. it may run at 100 but it's not right, there underpowered as it is, I dread to imagine what 100psi compression is like!
trx300's will crank and run at 100 psi, anything lower than this ?, they just won't act right. 170-180 will run a long time before it needs a top end job, take my word on this !..lol.
 

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I agree, it will run, but it's not right, hence Honda specifying 178 to 206. I advised the OP as per the FSM specs ;-)
 

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I agree, it will run, but it's not right, hence Honda specifying 178 to 206. I advised the OP as per the FSM specs ;-)
and your right, Honda specs WANT you to replace them..lol. his psi is fine for a long time, not arguing your point, your point is valid, my point is, he can run that trx300 for a few more years before he needs to do a top end job :).
 

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Here here.. We'll agree to disagree then lol :)
 
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