Compression Ratio & Gearing?
Posted: Wed Oct 26, 2016 11:28 pm
Hi all,
About to embark on full check over and rebuilds of my '56 and '55 (short stroke and long stroke respectively) engines. The '56 puffs a bit of smoke (maybe valve guides) and the '55 blows enough to look like a steam locomotive, even after a new piston, rings and cylinder sleeve.(suspect a broken ring or worse).
Q: The '55 G80CS was fitted with a JP 8.5:1 CR +0.020 Piston.
1. What is the weight of the standard piston supposed to be? (where do I find this information for all models?)
2. What do you guys think is a 'happy medium' compression ratio to use for general road use to balance engine longevity and power?
3. I'm running stock gearing. (18T Engine sprocket) What engine sprockets are you guys running for good road use for modern speeds?
3a. Is there any benefit in a lower CR for higher gearing? After all, the engine is designed to plonk along not, Rev.
I'm beginning to think, the higher comp piston fitted, has although given more 'power', but it seems to die on hills and doesn't really 'hum along' unless at 50mph. I'd like it to be happy to hum along at 60mph all day.
Q: The '56 G80CS is an unknown quantity until I pull it down. (Short stroke, AMC gearbox and clutch with cush drive) This bike has hideous vibration, so want to sort it (refer other thread) and am thinking it's either piston, balance, incorrect flywheels or something. Only way to sort it, is to pull it down.
1. What is the weight of the standard piston supposed to be?
2. Same as above #2.
3. Best road gearing? Running 20T Engine Sprocket.(19T standard?)
I'm thinking, I'd like to build these engines with longevity in mind, with the ability to be happy at 60mph.
I have a 2100 mile trip in planning to the 2017 Jampot Rally, so want the bikes to be WELL sorted and happy to plug along all day.
Cheers
Marty
About to embark on full check over and rebuilds of my '56 and '55 (short stroke and long stroke respectively) engines. The '56 puffs a bit of smoke (maybe valve guides) and the '55 blows enough to look like a steam locomotive, even after a new piston, rings and cylinder sleeve.(suspect a broken ring or worse).
Q: The '55 G80CS was fitted with a JP 8.5:1 CR +0.020 Piston.
1. What is the weight of the standard piston supposed to be? (where do I find this information for all models?)
2. What do you guys think is a 'happy medium' compression ratio to use for general road use to balance engine longevity and power?
3. I'm running stock gearing. (18T Engine sprocket) What engine sprockets are you guys running for good road use for modern speeds?
3a. Is there any benefit in a lower CR for higher gearing? After all, the engine is designed to plonk along not, Rev.
I'm beginning to think, the higher comp piston fitted, has although given more 'power', but it seems to die on hills and doesn't really 'hum along' unless at 50mph. I'd like it to be happy to hum along at 60mph all day.
Q: The '56 G80CS is an unknown quantity until I pull it down. (Short stroke, AMC gearbox and clutch with cush drive) This bike has hideous vibration, so want to sort it (refer other thread) and am thinking it's either piston, balance, incorrect flywheels or something. Only way to sort it, is to pull it down.
1. What is the weight of the standard piston supposed to be?
2. Same as above #2.
3. Best road gearing? Running 20T Engine Sprocket.(19T standard?)
I'm thinking, I'd like to build these engines with longevity in mind, with the ability to be happy at 60mph.
I have a 2100 mile trip in planning to the 2017 Jampot Rally, so want the bikes to be WELL sorted and happy to plug along all day.
Cheers
Marty