Up Jet?

[dude]

I have a couple of pipes Iam going to play with. One is a MRP the other is a NextR. I put the MRP on and ran it down the road once. It pulled better, no top speed gain. Iam running everthing stock except for the clutch. Didnt run it long to get a plug reading (old plug) How much should i Up Jet for these pipes? It has a 70 jet. I was told they look like old Honda jets are they? Vento

[90GTVert]

I don't know what to tell you about a standard upjet for a pipe. I just buy a box of spark plugs when I think I need to tune. Put in a new plug and run it briefly. You should be able to get a good idea of what's going on that way. I never upjetted when I put the pipe on the 70 or 90 and my plugs still looked alright, but you may not have the same experience. I'm not sure what jets to get for stock carbs either. I know you can get replacement jets from your local yamaha dealer form an air cooled Zuma or Jog. If you have spare jets, or even if you don't I guess, you can drill the stock jet. You need to have jet drills and a way to drill the jet straight though. If a jet is drilled out of round it could actaully flow like a much larger jet.

[rallyrrr]

dude

NextR will probably get you a few mph on top end. Maybe 5 mph. If you don't mess with your air box you probably won't have to upjet. The NextR will knock your bottom end down. I dropped my rollers from 7 to 4.5g with good results. Stiffer contra (yellow) is recommended also. Carbon fiber reeds give you a noticeable bump up there too.

[dude]

Ive ran it down a hill it 50mph with no more mph.(like it hit a wall) Its hit 50mph on flat ground alot. Since then Ive added a Malossi Var. 6gr#'s (Stock Var. 4gr Dr pulley's weights worked great) -Torsion Controller with stock spring-1500 clutch springs. I am looking for reeds. Would like to find diff thinkness at a deal.

[dude]

I ran the MRP pipe some more. (on the Zip) With the stock jet(70) The plug looked good. Chocoolate Brown. I picked a good 5mph. Change to the 2000 clutch springs. Needs a little more tuning. ran it down a slight hill. Iam guess it was going close to 60mph (speedo stops at 50) Never check it with GPS but beside a car a while back.

[90GTVert]

Sounds like it's working out pretty well for you.

I was just admiring your avatar and thinking. I think I've still got a stock crankshaft/connecting rod and I doubt I'll ever use my 52mm piston again. I may have to make myself a "statue" like that someday.