On Saturday I bolted on stock tires and rims which are studded and headed to Frenchmans Bay in Pickering Ontario for some 1/4 mph testing with a radar gun.

i have a 87 Fourtrax 250R(that has been collecting dust for years and now coming out again) with a locally ported cylinder and head work. A 36mm round Keihn carb and a 10+year old FMF pipe (dirtbike style looking). The front sprocket has been changed to a 15 (up from a 13) for a little more added top-end gearing.
The 2 ice runs were snowplowed a day earlier so traction was about 75% to start out.
On our initial passes, we managed a 68.4mph but had some issues such as an overly fat carb. We decided to switch the needle jet from the middle position to the 1st (leanest) moving the clip 2 positions. We also pulled off the uni-foam filter, but still running the airbox with no lid.
It picked up and it ended up running a 71.6mph. We still have carburator issues and could not pull 6th gear strong. Also after running up and down numerous times, the track started to get loose and we were spinning the tires going past the radar gun.
Having problems with 6th gear, we decided to try a few 5th gear runs.. 72.2 MPH!! We decided to call it a day and fix a few more issues before testing again, hopefully within a day or two.

Some changes that will be done before the next test session is to re-seal the pipe at the silencer and at the cylinder head as it was having fairly major leaks.Also noticed a smaller diameter piece of exhaust at the head to me looks like some type of exhaust restriction. It has been ditched. I will also ditch the reed-spacer to see if that helps. Another thing is it lost alot of studs! I will have to re-stud the tires as there's not many left!
I did a compression test and its at 170psi. I am going to try the double gasket trick for the cylinder and get the CR head gasket. I will then check the compression again from there and see if I need to mill the head down. I would like to get it up about 180-185 and still use pump gas.
The carb will also go in for a 2mm bore job.
Once this 'old' combination is max-tuned, I will start adding new parts. Such as the FTZ in-frame REV pipe. I beleive the old FMF pipe I have is a mid-range style, and swapping it out for FTZ REV pipe will hopefully get the bike to pull 6th gear into the powerband. I just couldn't get 6th to reach powerband and pull for top-end.

Just a little report from just outside Toronto, Canada. Looking for 75+mph next time out and hopefully 80+mph once a few parts go in!

Later dudes.

 

That is too fast!!!

Just kidding. Sounds like fun.