I was wondering how HMF pipes compare to Sparks pipes on a Raptor
I do a lot of mx track racing and some sand riding and very little trails
I was debating if it is worth the money to get a Sparks pipe instead, or if the HMF is too close in comparison to justify buying another pipe?

 

The hmf is a good low and mid pipe, but max hp gains are around 8hp. Sparks is around 12. IMO you would be better off doing a little engine work for the money, you wont out flow the HMF without some big internal changes.

 

thats what i figured i am planning on a 686 sometime this summer and while the motor is out im gonna gusset the frame and have it powdercoated

do you thin a 686 will withstand a lot of mx riding
the majority of my riding is on the track
what compression do you think is good for that
i mean im not lookin for all out top end power but i want a very mx raceable motor with not a radical compression

 

I would say an 11:1 compression would be fine, but a 12:1 or so would give you more low end if you dont mind running a good gasoline. Cam selection and head porting are going to be more vital than the compression ratio IMO.

The 686 holds up great on the track, UBETRUN started with one of those and moved up to a 730 later.

 

HMF is a decent pipe but their are so many better others, for you comparison i would get the sparks without thinking twice.