this doesnt sound right?!

[300rman]

my 84 R engine had about 100-120 lbs compression (can hardly read the damn gauge.). well, for as stiff as this thing is to kick over, and as well as the thing runs, this couldnt be right, could it? the gauge probably lying to me?

[cr480r]

are you using an adapter that has a full 3/4" of threads? It makes a big difference. Does the directional valve hold over 120 psi? You might try the guage on a different engine to see... Are you crankin the engine with the throttle wide open?

[bigreddaddy]

If it runs good then why worry about the compression?

[cr480r]

If it runs good then why worry about the compression?

For future reference so you test the condition of the ring seal...

[300rman]

are you using an adapter that has a full 3/4" of threads? It makes a big difference. Does the directional valve hold over 120 psi? You might try the guage on a different engine to see... Are you crankin the engine with the throttle wide open?

nope, i am pretty sure it is short, maybe a half inch?

you lost me at the directional valve? the gauge goes to like 250 or so.

as for trying it on a different engine, no good, as i have nothing to compare it to?

nope, no crankin with the throttle opened at all.


For future reference so you test the condition of the ring seal...

that, and im trying to figure out if i need to run a higher octane than 93 pump......

[brapp]

does it knock when runnign or under load if it doesnt detonate your fine.

[Erics350x]

You have to have it at wide open throttle to test and crank it over several good kicks.

[cr480r]

nope, i am pretty sure it is short, maybe a half inch?


By using the hose adapter with only 3/8" reach it adds volume to the chamber during testing that would normally be taken up by the spark plug... so be sure to use same guage set-up next time for comparison, or else your results will vary...


nope, no crankin with the throttle opened at all.

Thats why your guage readings are so low... Always test at wide open..


you lost me at the directional valve? the gauge goes to like 250 or so.

Most guages have a pair of shraeder valves in them that traps the pressure in the line... if one of the valves is only holding 120psi for example, then thats all that will show on the guage even if the engine is putting out 200psi...


im trying to figure out if i need to run a higher octane than 93 pump......

Too many varibles for cranking pressure to be an adequate indicator of fuel requirement... My Lt would run on pump fuel at 215psi with no audible detonation...

[lndy650]

some gauges have really long hoses my tecate read 225 with a short hose gauge and 200 with the long hose gauge. you have to determine your compression ratio to know if you need race fuel... always good to measure the squish too.

[bigreddaddy]

that, and im trying to figure out if i need to run a higher octane than 93 pump......

Oh ok. I was just wondering since you've had so many problems with it before I figured you would just be riding it HARD. Good luck with her.

[300rman]

does it knock when runnign or under load if it doesnt detonate your fine.

well thats just it. i dont know. after it gets warmed up, the mid-throttle range gets this funny clunk/rattle/i dont know how to describe it, other than it kind of reminds me of minor piston slap. but only when its warm, and only in the mid-throttle range.



Oh ok. I was just wondering since you've had so many problems with it before I figured you would just be riding it HARD. Good luck with her.

well thats the problem. i was, and thats how i found my main is too lean. everything else is dead on, so the plug gets a nice color, but use WOT for more than a few seconds at a time, and the plug slowly goes white......
long story short i locked the turd up......rippin along, then STOP. still has the same compression/kick feel as before, and still runs awesome, so i got lucky.......





and yes, i know cranking pressure isnt the only determining factor. The owner of PR Racing has built 2 strokes that crank about 260-280 pounds, and still run on a 50/50 mix with no problems at all. thats NUTS.

[TJ BIG DAWG]

The owner of PR Racing has built 2 strokes that crank about 260-280 pounds, and still run on a 50/50 mix with no problems at all. thats NUTS.

compressoin has no bearing on fuel/oil mix

[cr480r]

compressoin has no bearing on fuel/oil mix

he is refereing to 50% race gas/ 50% pump gas... not pre-mix ratio


well thats just it. i dont know. after it gets warmed up, the mid-throttle range gets this funny clunk/rattle/i dont know how to describe it, other than it kind of reminds me of minor piston slap. but only when its warm, and only in the mid-throttle range.

try lowering your needle clip position... if that doesnt work then its probably time to buy some good fuel...


i know cranking pressure isnt the only determining factor. The owner of PR Racing has built 2 strokes that crank about 260-280 pounds, and still run on a 50/50 mix with no problems at all. thats NUTS.

the KX engine in my tecate cranks 270psi... it runs well on a 50/50 blend... it might even run ok on pump... but I havent had to try that yet....

[300rman]

he is refereing to 50% race gas/ 50% pump gas... not pre-mix ratio

thanks for clearing that up.




try lowering your needle clip position... if that doesnt work then its probably time to buy some good fuel...



well, i need to richen the main first.

now, you are referring to dropping the Clip so as to RAISE the needle and richen the circuit, correct?