TOPIC:

Ok, I'm getting closer to finishing the 810cc 650, and have a question. heres the situation first: Im using the stock 650 intake boots (made for the VM 24s) and Ill be using a set of VM 28s. I put a tiny bit of oil on the intake boots, and they slipped over/onto the larger carbs just fine(no need to enlarge the boots to fit like previously speculated) but with the boots off of the head, I can notice that the boot between the carb and the head has a slightly smaller inner diameter then the inner diameter of the carb. my question is, how shouid I go about "porting" the intake boot so that the inner diameter is the same as the carb so as not to restrict flow? will a die grinder work on rubber? sandpaper? utility knife?
ps Im doing some light porting to the head if that influences your answers
thx a lot!
Scott

I wouldn't recommend "porting" the intake manifolds like you're considering doing. Since that would essentially rough the inside surface up, it might alter/disturb the airflow enough to create a rich running condition. Or worse yet, depending on how much material is removed it could cause vacuumm leaks and a lean running condition. Plus, if the roughed up surface has any loose particles left on it that can be drawn into the cylinders, I'd wager that although it may not be catastrophic, it sure wouldn't be beneficial either.

I'd suggest just buying new manifolds to fit the bike that the VM 28's came from, especially since you said you're doing some "light porting" to the head anyway.

Sandpaper drums in a Dremel tool should work.

A die grinder will probably work, but the rubber may load up on the grinding wheel quickly. Also, you'd have to be very careful not to remove too much rubber.

Try to get a smooth transition to the intake port in the head.

If you burn through the rubber, you're done and have to go buy a set of 28s.

Post edited by: vegasjetskier, at: 2006/09/09 20:07

when you port a head you want to leave intakes a little rough to promote keeping fuel/air mixed as it goes through ports.

i'm doing the same thing. does anyone make an adapter or different manifolds to make larger carbs fit on a 650?mine had 34 cv's on it when i got it and now i'm running 26's. i had to elongate the holes to mount them. is there a better way?

If I was going to do it I would use a wheel cylinder hone for drum brakes. Also, make sure you hone all 4 boots to the same size, but that's sort of obvious.
Ride Safe,
Les

I was out working on the bike today/tonight, and pretty much figured out the carb boot problem. I used a very small utility knife and a small grinding/cutting wheel in a drill to match the IDs of the boots to the carbs. I took my time and the first 2 turned out pretty good. (do the other 2 tomorrow) the finished surface isnt close to being as rough as the actual intake port itsself, so I think it will be just fine.
I did most of the porting for that half of the head as well, had no idea it was such a looong process, but its turning out great so far (at least thats what I think )

i'd love a pic of the bike that you describe in your signature...

Post edited by: requiem, at: 2006/09/13 16:41