ET: Engine (Twin) Too much compression ?

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BigEd

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No. Turns over fine with clutch disengaged and clutch engaged and plugs out.
Do you mean:
  1. With the clutch lever pulled in the starter motor turns over OK as there is no connection to the primary drive?
  2. With the clutch lever out the starter can turn the engine over if the plugs are out, i.e. no compression to work against?
If the clutch is definitely not slipping under load could it be a problem with the sprag clutch under the kick-start cover?
 

Howard

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Try a jumper lead from the battery earth to the motor, sounds like a bad earth to me.

It's not earthed through the body, it's got a 70A earth cable back to the battery, but I like your thinking - I'll start at the earth brush and check everything again.

All the gears and spragg clutch are good. Cleaned regreased and refitted.
 

Howard

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Do you mean:
  1. With the clutch lever pulled in the starter motor turns over OK as there is no connection to the primary drive?
  2. With the clutch lever out the starter can turn the engine over if the plugs are out, i.e. no compression to work against?
If the clutch is definitely not slipping under load could it be a problem with the sprag clutch under the kick-start cover?

1. yes
2. yes - spins everything quickly with no sign of strain until I put either front, rear or both plugs in.
3. no - it turns until the motor stalls and the cables get hot. I've got a car battery to it now with 30A jump leads and they start to smoke when the motor stalls.

I hope I'm soon going to look very silly and find something I've overlooked, because I'm running out of ideas.
 

roy the mechanic

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If the leads are getting hot, it sounds like the starter motor is drawing too much current. Ideally you need to come up with a heavy duty ampmeter to measure the starter "draw". I'm sure Mr Grosset will be able to tell what the draw should be. If I'm on target the motor is finished.
 

Howard

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If the leads are getting hot, it sounds like the starter motor is drawing too much current. Ideally you need to come up with a heavy duty ampmeter to measure the starter "draw". I'm sure Mr Grosset will be able to tell what the draw should be. If I'm on target the motor is finished.

Swapped for new motor - same problem.
 

clevtrev

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It's not earthed through the body, it's got a 70A earth cable back to the battery, but I like your thinking - I'll start at the earth brush and check everything again.

All the gears and spragg clutch are good. Cleaned regreased and refitted.
Regreased ? The amount of grease required is merely enough to just SMEAR the faces of the sprag. Any more than that is enough to stop the pivoting of the sprag inserts, that in turn means that the unit will slip , and not drive. Any further problems send the unit to me and I will check out.
 

Comet Rider

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Howard,
Although I maybe criticised by Trev, I feel that the gauge of the cables used by F Grosset is to light.
I re-wired a bike for someone a few years back, and went for much better heavier gauge wires and had no further problems

Best of luck
Neil
 
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