[Redy]

Anyone know what is the stock 450r cylinder compression ?

 

[KBR]

Do you mean PSI at the head?
If so, its almost impossible to compare with any one else. Gauges differ, altitude differs, and there is a decomp in the cam.
I think mine read about 90psi @5000feet with a Craftsman gauge, with HRC cam.

 

[lukester720]

10.5:1 If you just mean the piston.

 

[Redy]

Thank KGB!

I have 140 psi .... but I have stock cam.

 

[TRX450rlude]

Originally posted by Redy@Jun 3 2004, 08:29 AM
Thank KGB!

I have 140 psi .... but I have stock cam.

thats a huge difference from the 90 PSI recorded earlier....I dont think a different cam would cause that....It sounds like the guy with 90 PSI's checked his compression with the valves partly open.....or something....I know that impossible to do really....so what gives....

 

[lukester720]

Due to the bigger cam (the HRC opposed to stock) the pressure in the cylinder would be reduced due to the valves opening further for longer. Redy didn't say if he had an aftermarket pipe or not, but KGB has an lrd which would flow better than stock which would alleviate some pressure also.

 

[TRX450rlude]

Originally posted by lukester720@Jun 3 2004, 09:31 AM
Due to the bigger cam (the HRC opposed to stock) the pressure in the cylinder would be reduced due to the valves opening further for longer. Redy didn't say if he had an aftermarket pipe or not, but KGB has an lrd which would flow better than stock which would alleviate some pressure also.

I had no idea.

 

[KBR]

I could be wrong, on 90psi. I will check it again. When you check the head pressure, you should hold throttle wide open, remove air filter, and kick it over abotu 5-6 times.
As stated before, gauges and elevation make a big difference. As do cams, bigger cams, hold the valve open longer, and farther, therfore usually lowering the comp ratio.

 

[DN1911]

you can't lower comp ratio unless u change the head, piston, cylinder, or crank stroke. directly. now will changing cames filters and exhaust affect the cylinder pressure i don't know.

 

[PICKLES]

exhaust and the rest of the things will all change engine pressure because you are changing the time that the pressure is released and you are letting more air/fuel go threw the motor. but as I said I read it on here but it made sence to me and I popped it into here.
-good luck

 

[travis fulton]

anyone know how much cylinder pressure with 15-1 up to 16-1 ????????

 

[Mitco39]

I have about 90...however I cannot kick anything more then 140...so I set my decomp to 90 because it was the middle between hard kicking and hard starting....starts great.

Agian everyones decomp is different soo its impossible to test and get the same results. Try turning off the decomp and kicking it...thats the only way to get ture compression however i think you may need to pull it behind something to crank it over.

 

[450RRR]

actually.....to be honest with you.....if your talking about checking your compression......unless you have disengaged your auto decompressor.....you should all have the same readings for the same model bike....irregardless of which cam you use......IF you have reajusted your decompressor for the proper cranking PSI after making mods to your engine.....

the 04/05 machines are suppose to have a cranking psi of only 108psi...

the 06 kicker should have between 139-144psi......why its different than the 04/05 models I have no idea.....unless they used the same clearances and the difference is due to the higher comp 12:1 piston.......which wouldnt make any sense to me cuzz you can easily adjust it back down to 108psi if 140 is a bit hard on the leg....

and the 06 E start is way down at only 50-56psi.....

I dont know about the kickers.....but I am assuming the only reason why they have a decompressor is because it would be way too hard to kick one over w/o it......as for the E-start....that is definitely the case...anything above 100psi on the E-start and she wont turn over.....I found it starts best set at about 85-90psi...instead of the honda specs of 55psi...

if your wanting compression ratios......the 04/05 is 10.5:1...the 06 is 12:1

info only....Greg

 

[Blackie]

Pulling your bike is no different than kicking it over. The Decomp remains in effect until you reach the RPM required to sling the fly weight.


If you could manage to pull it at a decent speed and maintain traction. You could get an accurate reading ( I think :dunno: )


I dont know if I would try this though :ermm:

 

[Mitco39]

NoNo...first you disable it....

You know by increasing the clearance till it has no effect on the rocker arm....that way at any RPM it will show your compression...

Or am I wrong?

 

[Blackie]

Originally posted by Mitco39@Jul 18 2006, 06:22 PM
NoNo...first you disable it....

You know by increasing the clearance till it has no effect on the rocker arm....that way at any RPM it will show your compression...

Or am I wrong?

[snapback]262103[/snapback]​

Uhhh.... :dunno: Yeah... I guess that prolly would work :blink:


Still.....I am not sure your bike would turn over. Maybe with some American Racers on pavement :dunno: But I dont know....



I can pretty well guarantee my bike would drag the tires :lol2:

 

[450RRR]

That is one good way to disable to decomp.....increase the gap...

but yeah, not sure she would turn over....whether kicking or pulling or whatnot.....

jmho...Greg

 

[Mitco39]

Hmm...yea I never tried it...just thought it may work...