Fresh Top-end..Lost of compression!!

[blasterbogger]

Alright i have built a fresh motor and broken in very well... i used to have 120psi and after the break in, i had 145psi.After a weekend ride i came back home and checked my compression and was at 135psi i was pissed offX(, i dont know what caused this.. but i rode it pretty hard..

 

[Awk08]

i've had similar results, and just said fug it !!!!! it runs like a raped ape, and when it doesn't anymore, i will rebuild again

did you re-torque the head and base bolts after the break-ins???? check for leaks with a leakdown tester, could be a head or base gasket leak

 

[sheeblast]

ya retorque all bolts and nuts on the engine. also make sure your compression gauge is screwed in the same amount as before. i noticed a difference from 110psi to 120psi just by turning the tester in more.

 

[Awk08]

ya retorque all bolts and nuts on the engine. also make sure your compression gauge is screwed in the same amount as before. i noticed a difference from 110psi to 120psi just by turning the tester in more.

/\/\/\/\ thats interesting info

 

[sheeblast]

well think about it, when you put the tester in more, the area that becomes compressed is smaller.

 

[blasterbogger]

Thanks, ill re-torque everything down and and screw the guage in more and see if theres a difference.. Also is there a diy thread on how to make a leakdown tester.

 

[sheeblast]

i am sure there is, but to make it simple, find a PVC pipe that fit perfectly into your intake boot. and find a cap for the pipe. glue them together. drill a hole for a tire valve and a psi gauge. seal them. and get an exspansion plug for the exhaust. i have pictures of mine and it worked from for my banshee.

 

[Awk08]

here ya go.....................

http://www.blasterforum.com/do-yourself-20/build-use-leakdown-tester-10663/

and a vid on how to use it.................

http://www.blasterforum.com/do-yourself-20/leak-down-tester-video-33349/

also, guys have reported that a rubber expansion plug, with a wingnut on it, works well for blocking the exhaust port, available in the plumbing section

 

[blasterbogger]

thanks guys im going riding this sunday all im going to to is re-torque the heads bolts. and sleeve bolts too.. when im back ill check the compression if it keeps getting lower ill do a leakdown test. and if it dosent have leak ill just ride till it needs a new topend!!

 

[sheeblast]

here is my kit

 

[blasterbogger]

Looks pretty simple i guess i can get my uncle to do it for me.. he did it for his banshee i guess he can do it for the blasty.

 

[sheeblast]

it is simple, just need to make sure the fit is a good fit for the intake boot and you seal it up good.
but with an air compression, to get 6psi was a little to easy, so you have to be carefully not to blow it out. my dad was helping and the psi gauge shot upto around 25psi and it blow the pipe out. thankfully it hit him and not me.

 

[AcidRayn]

/\/\/\/\ thats interesting info

Take it for what it's worth. consider the source

 

[Awk08]

if you dont leak test before you go riding, you may need that rebuild sooner than you want, an airleak will fry that new top end !!!!!!

 

[blasterbogger]

i doubt it has an air leak the rpms dont hang and theres no sign of an air leak i have a feeling that my base gasket went out..

 

[royalt67]

i doubt it has an air leak the rpms dont hang and theres no sign of an air leak i have a feeling that my base gasket went out..

bad base gasket = air leak

 

[Awk08]

proven................only use factory yamaha base gasket, no vitos or k&s garbage, they will leak, guarenteed !!!!!!!!!!!!

 

[cole454]

Are Cometic gaskets good?

 

[darederek]

nope... yamaha only

 

[1bad442]

if u dont have time to make or buy a leak tester just take a handheld propane torch, start the quad turn the propane on without lighting it and put the tip of the torch around any areas that could cause an air leak if it has one the rpm will raise when u get to that area.