yamaha srx 700 low compression

YamahaSXR700

YamahaSXR700

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Joined
Jan 9, 2009
Messages
154
Age
36
Location
River Valley
hey guys, my bro has a yamaha srx 700, he bought it for cheap and the guy said he had rebuilt the engine in it, and um it looks like it has low compression, so we thorn the top end appart to inspect the piston and rings, and when we got the power valves out the mag side one was jammed in it, , and i forgot to mention that the guy before my bro, he did rebuilt it, because its not stock srx piston they are teflon coating on it on the skirts, and it looks pretty new, you see the cylinder has been owned, and could that power valve jammed up be a problem with the compression, we did a compression test i think it was 110 or less i cant remember, um and when u crank it to start it u see the diff of compression with antoher srx we had in the garage, any ideas
 
should run at 110. compression will not come up untill motor breaks in. motor will start and run with 90. stuck powervalve is not good but should still have started. might need some gas in the cylinders untill the fuel pump gets re-primed.
 
the engine runs, but like we didnt beleive the guy that he said when he optu new pistons and rings, cuz it looked like it had low comp. and it did a bit then when we opened it up tonight, like its not new but its new u know what i mean u see it has been changed
 
oh ok. those pistons are spx (i think). got a set from ebay for my brothers viper last season. supposed to be the same quality as oem yammy pistons according to all the research my brother did.

it will have lower compression #'s for at least the 1st 10hrs of operation or untill the rings seat to the cylinders. took me that long with my xt when i put it together this spring for the rings to seat in for full compression.
 
every compression tester reads different, so don't get too caught up on the 110psi reading you were getting. i bet if you tried 4 other testers, you would have 4 more different readings. those pistons you are describing, sound like SPI pistons that are made in taiwan.
 
i rebuilt my srx with those spx pistons this season, hasnt broken in yet was around 110 compression as well .sled works awsome so far so good ill recheck it after a few tanks my tester was 15 bucks so im sure its not that good , these pistons are cast which are like oem , wisecos are forged, both have there benifits i would say forged for a lake racer , ill probaly go with wisecos in my rmk 800 though, but spx were cheap whole kit for top end was 280 shipped including complete gasket set
 
Mikeast... where did you get a deal like that for 280 for a while top end kit? it includes rings pistons and gaskets???

we got peged with 400 n something for 3 spx I think pistons top end gaskets and rings... was for a mach z 800 touring though
 
mikeast said:
got it on ebay , ill try to look up name of company in my ebay account
Click to expand...

ya from buying oem, pistons ,rings, gaskets, clips everything needed to rebuild it saved me 400 dollors i know we pay way more up here though for oem parts then most of probaly do in the USA though, i was lucky my bottom end clearances on the crank were like brand new for a sled that had 6500 km :letitsnow
 
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