After all the trouble starting and plug fouling it seems it is the main bearings so seals as well.

Please see pic attached.

Discernible movement when levered under the magneto so engine re-build it is.

The pictures in my manual aren't good. They mention the 12, 6mm nuts securing the crankcase halves and not to loosen the illustrated one as it secures the friction pin though this does not apply to pre '76 models. I can't make out which one they mean.

Can anyone shed any light on this? Also any advice on pitfalls to avoid gratefully accepted.

 

Cheers Neil

Edited September 24, 20169 yr by netley

You just need to undo all the small nuts on the and the allan screw just behind the front engine mount (on the picture0 I left the gears on one side and crank  on the other It is a long time since I did one  about 40years I think

Back to the garage then.

Cheers !

Where have the rest of the balls or the cage gone ?

When I can finally split the crank cases I will find out !

Any tips for splitting the cases ?

Follow the manual. Make an engine support if possible (see, page 3  #38). And use a puller, (see page 2 #30).

 

http://www.trialscentral.com/forums/topic/57939-rebuilding-my-bultaco-159-engine/page-2

Edited September 24, 20169 yr by guys

hit it with  a big  hammer  that  normaly splits the Engine Ah only joking I just undo alloy the half crank case nuts and the small Allen bolt hat the front Engine mount I just use a hot Air gun to heat all around the centre crank with a hide hammer gently tape the crank shaft then it should come apart ii just rest the Engine on too blocks off Wood. obviously make sure all nuts or off and front sprocket ignition flywheel all the clutch needs to come off crank seal holders.

Edited September 24, 20169 yr by bondy

As already stated heat is your best friend for disassembly and reassembly. I would suggest making up a tool to help split cases. That is one that pushes crank shaft and gear shaft out of bearings to separate cases.

Where have the rest of the balls or the cage gone ?

That's what I was thinking!

The pulverised swarf in the bottom of the mag. housing says it all !.........

NEIL

 

Your friends will be here to help.

 

I use an old Clymer manual, it will be of great help, the best is you are on a 5 speed Bultaco & for me they are the BEST.

 

Good Luck

 

Larry

I think the swarf is from where the magneto had been catching on the housing !!!

Suprused it ran at all.

It seems it was the plastic bearing holder that had disintegrated in the left hand case. Work will recommence after the weekend.

Edited October 1, 20169 yr by netley

Hi Netley. To reassemble the engine you will find it a lot easier to remove the neutral stop which is the 19mm bolt on the left hand case with the spring loaded rounded thing on the end of it. It also makes everything a lot easier if all the gears are in the left hand case and not the right hand one where they are now. Use a few dabs of grease on the centre gasket and have it on the right hand case. They usually go back together really easy. Don`t forget the small washer on top of the kickstart gear. Graham.

Re-built crank back today with all new con rod and big/little end bearings. Now just need some time but at least I didn't buy a BMW GS.

Saw this one in the shop, 60,000 miles !

 

Edited October 10, 20169 yr by netley