Hi everybody

I'm in the process of rebuilding the engine of my Sherpa.

I need (among many other parts) a new piston kit.

Does anybody have experience with the Italkit pistons from In Motion?

Or does some one of you guys know from a secret stash of original Mahle pistons? I need a 84.00mm piston.

 

The last piston I bought was for the 151 engine I have in my 199B. I bought a Wiseco from Bultaco Classic in the USA. I think Bultaco Australia still has some Mahle pistons. The ones from In Motion are probably fine too. There is another place that has some but I haven`t heard from him in a while and he isn`t answering the phone lately so I`m not sure about him. Graham. 

The ones from inmotion are very good. I have a brand new MAHLE in the box but it's 84.75 i also got a new MAHLE piston for my 199b witch is in and awaiting to put in the bike. I can get MAHLE pistons but need the port holes putting in and the skirt needs trimming down as there pursangs pistons.

Edited December 10, 201510 yr by bondy

The last piston I bought was for the 151 engine I have in my 199B. I bought a Wiseco from Bultaco Classic in the USA. I think Bultaco Australia still has some Mahle pistons. The ones from In Motion are probably fine too. There is another place that has some but I haven`t heard from him in a while and he isn`t answering the phone lately so I`m not sure about him. Graham. 

 

Thanks, but I fear the shipping costs from Australia might be a bit high.

 

I've also contacted Gilles from France ( http://trial-classic-bultaco.fr/index.html ) but he only has a few Mahles left. 

 

Guy

The ones from inmotion are very good. I have a brand new MAHLE in the box but it's 84.75 i also got a new MAHLE piston for my 199b witch is in and awaiting to put in the bike. I can get MAHLE pistons but need the port holes putting in and the skirt needs trimming down as there pursangs pistons.

 

Thanks Bondy, that's good to know about the In Motion pistons. (although I never really had any doubts about the quality of In Motion's parts ;-)

 

Ok i did also was lucky and got a MAHLE piston for my 199A but the ones from inmotion are just as good in my option i just put 1 in another 199b am restoring for some 1 that 1 as a teflon coating on it like a gas gas piston.

Edited December 10, 201510 yr by bondy

This is how the piston pin bearing was mounted.

Some one forgot the two spacers apparently:

 

 

Maybe that explains the  blue heat marks on the pin:

 

 

Although the piston - cilinder clearance is at the maximum, the rings were still doing their job, hardly any blow-by deposit on the piston.

 

 

Yes there should be 2 spacers on the MAHLE piston the new typ don't have them they don't fit so you have a 30mm small end bearing.

Guy,I have run Wisecos in my Pursang and haven,t ever had a problem.It gets hammered on pretty hard and has turned some pretty high rpms with a missed shift here and there.Also,check out Wossner pistons from Germany.I don,t know if they make one for the Bul,but I purchased one for my Maico and it looks to be very good quality.

Wössner pistons are very good.

For original pistons you might ask Orlando Calonder in Switzerland. Sadly the Swiss Franken exchange rate to € is a problem.

How does the lower con-rod bearing work. If you turn the crank with the con-rod the movement should be nice without any roughness or resistance, runnig freely but thight.

Piston pin looks very used.

Hi Scot

 

According to Wossner's 2014 catalog, they only have pistons for the Bultaco TS250, but thanks for the tips

Wössner do make custom pistons to your requirements.

They made the piston for my TR34 for a fair price.

Wössner pistons are very good.

For original pistons you might ask Orlando Calonder in Switzerland. Sadly the Swiss Franken exchange rate to € is a problem.

How does the lower con-rod bearing work. If you turn the crank with the con-rod the movement should be nice without any roughness or resistance, runnig freely but thight.

Piston pin looks very used.

 

When I turn the crank with with the con-rod it runs without roughness or resistance, but I would say it runs very loose, although I can't feel much radial play.

The axial clearance between the con rod and crank is 0.6mm, but I don't know how much it should be.

 

I think the pin looks very used (looks like it has been running hot) because the bearing was missing the two spacers, so the bearing could move sideways, resulting in the fact that sometimes only about half of the needle bearing was carrying the load.

 

The inside bearing race of the con-rod (at the small end) has the same discoloration as the piston pin and clear wear marks at the bottom (might also be from the fact that some times only half of the bearing was taking the load.

 

To be on the safe side, I'm going to replace the con-rod.

 

I had 3 new con rods pressed in earlier in the year he got them all with in 5% tollerance. Witch is good.

I had 3 new con rods pressed in earlier in the year he got them all with in 5% tollerance. Witch is good.

 

How much mm or inch is 5% tolerance?

 

I mean, what is the correct axial play between the con-rod and crank shaft?

 

EDIT   

 

I just found pschraubers answer:

 

a. Side-play / side clearance limit of the lower con-rod and the thrust washers is 0,25 mm.

b. Radial clearance for the bearing is 2,5mm in cross direction at the top of the con-rod!

c. If a and b is below the limits but the lower bearing feels rough while rotating the con-rod replace too!

Repalce always lower con-rod pin, thrust washers and con-rod together, if you detect one of a, b or c.

Edited December 11, 201510 yr by guys