>>>>180 psi trail motor, Looking for a cold setup. <<<<

[blasterbogger]

Hey Guys , You all know i recently built my bike and i just finished breaking her in not too long ago but funny thing is i never attempted a compression test . Due to the lack of riding i just noticed some weird noises coming out of my engine while a quick ride around my house. Performed a compression test and my gauge read 180 Psi ! Here's the deal , i do alot of trail's and i wanna try and keep my motor cooler . Since my head is cut and theres so much compression i think the motor would run hotter after reading in the forums. Im thinking about running b9es plugs and retarding my timing. I really think the weird noises were detonation from running 93 pump gas , So i think switching to race fuel will be the best bet. Does anyone here run Avgas?

 

[Surfrjag]

thats some high compresion. you definitly need some race gas.. or you could get a thicker base gasket. whats your squish?

avgas might work for you but it will be on the edge still i think. retarding the timing i dont beleive will help.

 

[blasterbogger]

How can i check my squish? And if advancing your timing make the motor run hotter , retarding it make it run cooler? Hey surf , what is your compression on your drag bike?

 

[Blaaster]

Definatly need to get that octane rating up.

When you did the plug chops after re jetting for the mods was the smoke ring a straw or biscuit colour.

Retarding the ignition is going to loose you get up and go power.

What are your mods and what is jetting?

 

[Surfrjag]

in theory that would work but flame speed and compression are 2 different animals. my drag bike was about 160 but the head design was setup for high squish vilocity to run methanol. take a peice of solder and bend it about half the distance of the top of the piston, stick it in the sparkplug hole and try to get it to the left or right side to keep it over the piston pin so the piston. if you do it on the front or back it will rock the piston and give you an off reading. then roll the motor over slowly and let it squish the solder. then measure it.

who cut your head?

 

[blasterbogger]

Blaaster i was running a bit on the lean side . Running a 310 main and a 32.5 pilot. Toomey pipe , shaved head , bored .040 over , vf3 reeds , Home Port : Draggy/aggresive trail port.

 

[blasterbogger]

I Have no idea who cut my head . I believe it was cut 35 thousands of an inch . Probably more.

 

[Surfrjag]

im gonna lean towards more.. you can use a thicker base gasket but that will raise your port timing some. or put a different head on.

 

[blasterdemon7]

im gonna lean towards more.. you can use a thicker base gasket but that will raise your port timing some. or put a different head on.

Why not try a double OEM head gasket instead of a double base gasket ?

 

[Surfrjag]

i dont know how well the copper oem head gaskets would seal against eachother. i have never tried that but my guess is it would leak.

 

[blasterbogger]

Yea me too ^ . I will most likely add the extra base gasket and raise the cylinder , So theres no way i can keep my 180 psi.

 

[Surfrjag]

you can try running 110 octane with 180 psi but listen carefully for detonation... i would get it down some personally.

 

[blasterbogger]

Kinda funny , its like i have a drag motor in a freaking trail bike lol. Well , im going to raise the cylinder tomorrow buy some race fuel and get her going. Do i run pure 110 octane or 50/50 with pump gas?

 

[Surfrjag]

depends. post a picture of your head. maybe we can tell if its been modified. also be sure and do a squish test.

 

[blasterbogger]

Its not modified , just cut. But i can still post a pic tomorrow just in case. And i will try to measure my squish after i raise the cylinder.

 

[Blaaster]

Before I pulled down the motor and raised he cylinder I wuold be trying a 50/50 mix of 110 and pump gas, and bumping up the main to a #340.

I am not going to say that it will solve the problem, but it may be worth the try before wrenching.

 

[blasterbogger]

Your right, But will it be safe ? This is a trail bike and i think 180 psi is a bit extreme for my riding conditions. Even though i do alot of racing , i alsow want this motor to have a longer life span . I think have 160-170 compression would be better for me , still high but better than having 180 compression. Well , i still need more advice . If i can still run the 180 psi and have my motor run cooler i would stay with it. If not i would raise my jug by adding another base gasket. Also , anyone no the easy way of calculating what squish gives me what compression?

 

[Blaaster]

Blaaster i was running a bit on the lean side . Running a 310 main and a 32.5 pilot. Toomey pipe , shaved head , bored .040 over , vf3 reeds , Home Port : Draggy/aggresive trail port.

If you are running lean, then you will be running hot.

Increasing the octane and fuel in the mix should stop the detonation, and make the motor run cooler.

If you desire longlivety then it may pay to lower the compression some, how about fitting a different head and new gasket.

You say it has been ported! By raising the cylinder I believe you will upset the port timings too much

 

[2smoker85]

ok heres the deal 180 psi is not going to hurt anything, i am running a beastly motor with 180 psi and u should be able to get away with 50-110 50-93, u can run straight 110 too thats fine also with that high of compression, u should have no problems with that and the bike will last as long as u take care of it. clean ur filter before every ride,check for possible leaks, use a infrared temp gun to check the temp of the cylinder to make sure ur not running hot. as long as u follow the simple steps of basically taking care of the bike it will be fine. dont double up your gasket. just run higher octane and make sure its jetted correctly.

 

[Surfrjag]

By ported he means he raised the exhaust 1mm.
smoker isnt that a modified head you run? If the head is desined different to bring maximum squish veloxity down you can run higher compression with a given fuel. Boggers has just been milled. Stock head has a pretty wide flat squishband so its up to you bogger. Either have the head modified (best option) or raise the jug. Mho of course...