Bolens Diablo Rouge and Hus Ski Discussion Forums

Hi all,

I have a Mahle piston that came in a box of Diablo parts. It is a 75 mm piston like the Diablo Hirths use, but the top is domed upward. Therefore, I think someone bought it by mistake.

On the inside of the piston casted in the aluminum is 75L51+ and R012H. On the top is 75.86 and it is a 3-ring piston.

Anybody know what this could be for?

Hi Bruce,if the pin location and skirt length and shape is the same it would work but would be higher compression and would have to use better fuel. The Hirth and JLO motors are hemis so it shouldnt hit. It is good it has 3 rings and not 2.

Holy Cow - you really think so? I would have never guessed that. These Hirth engine's are a little fickle as is without jacking up the compression.

Would you know what other Hirth engine's it might fit?

I looked at the piston a little closer and I don't think it will work in the 300 Hirth. The pin height and skirt are certainly different than the typical 300 piston. I put it on eBay if anyone is interested. Also put a Tillotson HR 18A carb on ebay too.

Hi Bruce,Both of the two NOS pistons I have in original Hirth boxes have the same Mahle etc cast on the inside and 3 rings. One is part #014.21 with 74.85 on top (1st oversize?)and the other is part #014.21/10 with 75.36 on top (2nd oversize?).Perhaps they had one mold and machined to application? I do not have an original engine apart to compare to.Do factory assembled ones have Mahle casting?Mike8-)

Interesting. Don't know what to make of that.

Thanks for sharing Devil Dog.

Hey, I figured out the domed type piston is for the 52 R or 53 R. The 014.21 is standard 74.86; 014.21/10 is 1st over 75.36; 014.21/20 is 2nd over 75.86. I just took a piston out of one of the 54 R4 motors so now I know what they are supposed to look like. It is a Wiseco 040 2-ring. Are the rings available seperately from Wiseco still?