Garrett T25 Turbo Build

Wallywheels, you are running a single vm36 then right? The slide is larger than the vm34's so that will contribute to the slide getting hung up from boost pressure. The flat slide would have a much smaller cross sectional area and may eliminate the problem. Or you can run a stiffer spring. Could you maybe order a vm34 spring and run the 34 spring inside the vm36 spring? But then spring binding will probably be an issue.......take dimensions and hit up mcmaster-carr haha!
 
Quick update: Had a couple more test runs. I jetted up to 220 mains, 159P6 needle jets, 6DP1 needles in the 2nd from the bottom clip, 17.5 pilots. Comparing this tune to the initial tune (190 mains and same needles in middle clip position), still engaging a less severe stumble as boost comes on and a less severe stumble at wot (after going from 195 to 220 mains). After this last round of tuning the clutch is not transmitting the power. In gears 4-5th, at wot, between 6-7.5K rpm the clutch slips very badly and the engine over-revs wildly. Barnett clutch springs are installed. I checked the friction plates earlier in the build and they spec'd ok. I looked into the 8 disk clutch pack mod but I don't like the idea of removing material from the clutch basket. Opinions on this modification? Otherwise I was thinking of getting barnett friction disks from 650 central. I am waiting for this winter weather to finally end and start riding some more without freezin' my giblets off. BTW, the twin cities area is currently getting pounded with snow.....this is ridiculous :banghead:
I got myself a drift hd camera so I can finally make some riding videos without having to borrow my buddy's. Hopefully get a video up soon once the weather decides to cooperate.
 
8 plate clutch mod is pretty simple if you are familiar with using a lathe, mad not to try it. Sidecar racers have gone to 10 plate set-ups using this mod and thinner plates, they have 1000cc xs motors in their outfits. After that the only other avenue you would have you be to run a modified banshee lockup system or to build a dry clutch assy, which is a large time investment..
 
Cowboy, how well did the stock pistons hold up to the abuse you put them through? Are you running forged pistons now?
 
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Not really sure of the rpm's. Have a rev limiter on the bike that has a high limit of 9000 and have hit the limit. now the high limiter is turned off as soon as the bike launches.still stock valve train, but need to upgrade.just have to keep an eye on the retainers.
 
I took my spare clutch and marked it up to clearance it for 2 more friction disks. I am heading to platteville this weekend to meet up with some college friends again. Then Sunday we are going to earlville Iowa to tri states raceway where I hope to break my old time of 13.3 secs. Hoping to get the modded clutch in before then.
 
Congratulations! on getting it running "Looks Like Fun" just too much plumbing on the right limiting the entry in the tight twistys for me.
 
Thank you Jack! Haha yup! No more hard twisities. The physical setup limits the bike to straight line or left turns......drag racing or flat tracking.
 
Update on the 8 disc clutch: it's f'd. I didn't do a good job of chucking up the spare inner clutch hub in the lathe and was too aggressive with my passes and cracked the inner clutch hub. When I try to modify the current clutch I will be much more careful...... it is always a learning experience.
 
Ran the bike at tri states in earlville iowa and the best the bike and I could do was 13.039 @ 107.72 mph. Got my work cut out: the clutch was slowly getting worse as the day went on (really need to perform surgery on the clutch to fit more plates). Also, the valves float after 7k (stiffer springs and go back to stock valve tappet adjusters vs the elephant foot adjusters to lighten the valve train kinematics), lastly still need to dial in tuning. I was really hoping to dip into the 12's this time around but once these issues are addressed that should be easily done.
 

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