Scooterotica

muffster wrote:Always worth getting the compression tester out to check though. Any ideas what i should be getting? Its a 125 to 175 conversion.

Not sure of the reading for a 2 stroke but you should be able to feel definate pressure when you push the pedal down slowly. If it's starting and ticking over ok especialy when cold then it probably isn't a compression issue.

Was anything done to the ports or is it straight out of the box?

Muffster, where do you live? Must be someone nearby who could give you a hand. You mention Allstyles who are Pompey based. Does that mean you are south coast?

The head was donated to me by the guy who painted the scoot. I has the barrel rebored to fit an oversize 175 piston. i don't know the history of the head but i havn't had any porting done on it.

Cheers.

muffster wrote:The head was donated to me by the guy who painted the scoot. I has the barrel rebored to fit an oversize 175 piston. i don't know the history of the head but i havn't had any porting done on it.

Cheers.

But is the head profiled to fit the piston crown? What piston to bore clearance did you ask for when it was rebored? 3-4 thou is normally accepted as the correct gap. Was the ring gap checked too?

Hello dapper.
I actually live up in Bradford but i'm based in portsmouth. Gary at Allstyles has been very helpfull but it doesn't help having the scooter up north and only working on it at weekends.
As for bore clearance, i have to admit iv'e got no idea. I took the head and piston to a reputable machine shop and they did it for me.
I can't remember if i checked the ring gap. it was months ago when i built the engine up. is there anything in the book about it. I can't look in the book at the minute as i'm at work but i just built it up, as per the book says and it was pretty straight forward.
I'm and engineer so not totally stupid, but not i'm wondering if iv'e done something wrong.

Cheers.

muffster wrote:Hello dapper.
I actually live up in Bradford but i'm based in portsmouth. Gary at Allstyles has been very helpfull but it doesn't help having the scooter up north and only working on it at weekends.
As for bore clearance, i have to admit iv'e got no idea. I took the head and piston to a reputable machine shop and they did it for me.
I can't remember if i checked the ring gap. it was months ago when i built the engine up. is there anything in the book about it. I can't look in the book at the minute as i'm at work but i just built it up, as per the book says and it was pretty straight forward.
I'm and engineer so not totally stupid, but not i'm wondering if iv'e done something wrong.

Cheers.

To be fair, I doubt if ring gaps would cause your problem unless they were criminally big, I'd say the rings would need to be broken or stuck to make that much difference I THINK you should be looking at a gap of around 8-10 thou but I;m not enterely sure.

Starting to run out of ideas here It's not a badly set up clutch by any chance, which is slipping as you try to pull away? The clutch arm should be at right angles to the casing when at rest, and there should be about 1/16" free play at the clutch lever before the clutch is pulled in.

i'm quite confident the clutch is set up ok. I removed the rear hub at one point to adjust the angle of the clutch arm and it is in line with the stud on the casing. And there is a bit of free play at the lever, but these are both work checking again.
I've already ran out of ideas!!! But i will go over everything again, including the exhaust then post again to re-cap where i'm at.
However, i'm going to see the Specials tomorrow night so do't know how much i will achive at the weekend? :biggrin:


Thanks for reading.

Ok, i tried tweaking the timing at the weekend. I had it at 19 deg but thought i would advance it a little to see what the difference would be. So i tried it at 23 deg and it was a little better. Which is still not a conclusive answer but it runs as if it wants to pull away but hesitates then stutters a bit then picks up but i won't deliver the power smoothly. Full throttle in first and it's struggling.
So, any offers please folks. Can i try anything else with the timing, or is this a carb issue or electrical?

Thanks.

muffster wrote:Ok, i tried tweaking the timing at the weekend. I had it at 19 deg but thought i would advance it a little to see what the difference would be. So i tried it at 23 deg and it was a little better. Which is still not a conclusive answer but it runs as if it wants to pull away but hesitates then stutters a bit then picks up but i won't deliver the power smoothly. Full throttle in first and it's struggling.
So, any offers please folks. Can i try anything else with the timing, or is this a carb issue or electrical?

Thanks.

Your jetting will need adjusting to cater for the altered timing, I'd try it with a bigger main jet