186 special 115 main jet

[Billybiglift]

Hi,

I have a lambretta with 186 kit on it running in and the moment and when I remove the spark plug I still have quite a bit of compression there, also when I am riding scoot it feels like something is holding it back, and I need to rev quite hard to get enough speed up to change gear. Engine sounds spot on when in neutral, any ideas? I thought something might have been tight inside casing but am no expert

[Adam_Winstone]

If the plug is out then it will not be compression...! I'd be a little concerned about something else making contact or rubbing. I hate to say it but I'd not want to run the bike again until I'd determined what is causing the issue.

Adam

[ToBoldlyGo]

What sort of carb are we talking about Billy? If it's a 22 then 115 is way too small.

[Phil D]

Hi billy big lift
Can you fill in a bit more of the blanks
A bit more of the history of the motor ie newly built / who by?
Full spec of the motor ?
It's easier to pin point areas to look at / something's binding somewhere
When the plugs out there can't be compression it's an open cylinder if it's stiff to turn over something's Amiss .
As people have said I would not ride it as it needs attention .
Regards Phil.

[Billybiglift]

Sorry for being so vague, the engine was built by a very good builder and has all new seals, new barrel piston, chain, gearbox etc. I am sure it's a 28 m dellorto it is running, open mouth carb with no air filter. It was a swine to start so I took it to a grown up who changed the plug and jets and now it starts on the button no bother, it ticks over lovely but the chap who jetted it said there seemed to be a lot of compression once plug was removed. Engine is not run in yet, I have only done approximately 30 miles since rebuild.

[Phil D]

It's a bit confusing if it's a new top end I would expect it to have good compression .
Why not take it back to the engine builder.
You say it's holding back and have to rev it hard to get enough speed to change up that's not right.
Also you say it was re jetted to a 115 main jet that doesnt sound right either.

From what you say it's got brand new internals .
The engine builder should be willing to stand by their work?
I'm not trying to avoid the question but taking it to be fixed by someone else isn't right as
The original builder may have been sold a bad batch of parts.
He deserves the chance to fix the problem.
IMHO .
Phil