took it for a trip after 30m ish it suddenly lost power but stiil ran but sometimes stopped, fuel and spark seem ok, cant see any leaks, compresion seems ok crankcase seal perhaps?

any thoughts?

steve

Dodgy condensor, starts, sort of runs ok, has spark when you check.

Cheers Greg

If its sustained riding - like along a road - that you are talking about then the cause might be poor tank tank venting creating a slight vacuum in the fuel tank

Does the Alpina run a motoplat electronic ignition like the Pursang, the only time my Pursang let me down (surprisingly in everybody elses opinion) was after quite a lot of trail riding the main bearing on the flywheel side had developed enough play in it to mess up triggering the spark, It didn't get noisy or seem to loose compression but would only spark randomly.

 

Otherwise if it has a conventional ignition system and it runs ok when cold my vote is for a faulty condensor

greg do condensors go suddenly? how do you test?

 

fuf dont think so cos its done a few trips recently

 

giles im told it has elecronic ig and its been doing some trail work how did you know it was the bearing?

If it has electronic ignition, I would guess it has been changed as M99 is a M92 Sherpa engine for the most if not all

practical purposes, the mag flywheel is probably lighter however so one would assume points ignition and if so the

condenser as Greg points out is most likely the culprit, if it has points, an automotive condenser mounted under the

tank is an easy fix. If its electronic, then it is beyond my help.

Good Luck

Larry

 

greg do condensors go suddenly? how do you test?

 

fuf dont think so cos its done a few trips recently

 

giles im told it has elecronic ig and its been doing some trail work how did you know it was the bearing?

 

Embarasingly there was movement in the flywheel end of the crank when I took the casing off....

 

Yes condensors just fail with no warning

 

well ive wondered about the ign guess ill have to investigate, watch this space

You need to sort out whether it has a points ignition system [standard] or an aftermarket electronic system. I have used condensors off a lawn mower and a car while waiting for the correct one to turn up, and honestly couldn't pick a difference in performance. Condensors fail periodically with no warning, but typically when you check for a spark there generally is a faint spark which leads you to believe everything is OK. Its worth putting a new set of points in as well while you have the flywheel off.

Cheers Greg

havent had time to look at the ign but started with the plug its a NGK BP5ES according to the net if its elec ign it should have an r for resistor in the title otherwise might fry the ign!

does the team agree?

Ditto condenser,

Does it backfire, pop and bang? Hesitate and surge?

 

Condenser. 

 

Also, opinion seems to be to relocate it under the tank in the airflow.

 

Good luck.

got the outer cover off can see points which dont seem to move. what the favourite flywheel removal method?

Purchase a flywheel puller, money well spent, and are available on Ebay off various suppliers. I once had had an Italjet that had a similar issue - after removing the flywheel the Bakelite heel part of the points that ran on the cam section of the flywheel  had disintegrated.

Cheers Greg

know i need a puller but the whole holder thing is confusing straps, impact drivers special tools etc

I bought a flywheel holding tool from Sammy Miller probably about 35 years ago and it is still in perfect condition and been used on more engine rebuilds than I care to remember. Not sure of your location but the same tool I have is still available from Sammy Miller products here in the UK. (No connection just a happy customer after 35 years)

 

http://www.smproducts.co.uk/products/tools?page=shop.product_details&flypage=flypage.pbv.v9.tpl&product_id=729&category_id=27

 

 

Stuart