Thanks GP Tech, LLC. and Sportbike Track Time

Started by motomadness, May 12, 2003, 06:25:58 AM

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motomadness

As most of you know, at least those whom have seen me at the tracks in the MW, I have not been having a good season with the new bike.  That was until I hooked up with GP Tech, LLC (www.gptechllc.com) and missed a race weekend to participate in a track day with Sportbike Track Time (www.sportbiketracktime.com).

History -
Last year I bought an Aprilia RS250, had a lot of fun riding it, but was getting tired of losing races to SV's.  Over winter I told myself, make the Aprilia faster or buy a new bike.  I settled on the later and found a bike within a few weeks, a 1995 Yamaha TZ250, a real two-stroke GP bike.  At the time I was very pleased with my purchase.  That was until I started working on it.  I had to buy a lot of specialty tools and even had to take the motor apart and rebuild.  Hey it's a two-stroke, what else is new.  None of this bothered me too bad, but the first time I started it up and hit the track, I was extremely disappointed in how brutal the bike was.  I couldn't even keep up with the Aprilias.  After Road America I said something had to change for the better, or I am getting rid of the bike.

Now -
I took the motor out of the bike and sent it to my sponsor, GP Tech, LLC. (manufacturer of racing fairing brackets, thumb brakes and cool golf karts, distributor of many other racing products and two-stroke services).  They took the motor apart, measured it and rebuilt it with many new parts ($$$, but worth it).  

I spent last Friday night putting the motor in and finishing up the bike before the STT track day at Ginerman Raceway on Saturday.  All I have to say is the vibration is gone, I have plenty of mid-range pull (power wheelie out of T1), and I feel like they really put me on the right track with my engine setup.  Oh and I even practiced launching the bike.  Look out this weekend coming up at Gingerman.

Again, thanks GP Tech, LLC. and Sportbike Track Time.

motomadness

Oh and my Bridgestone slicks provided me with plenty of grip.  I can't wait to really battle test them this weekend.  

Let's pray for good weather.

dave333

It's always a great feeling when you finally get things sorted out and get a chance to let 'er rip!  Glad to hear things are coming together for ya...

motomadness

I can't forget the Ferodo brake pads.  I went through the entire system, put new lines on and even bead-blasted my rotors.   ;D

Chef

40. Our deepest fear is not that we are inadequate, but powerful beyond measure. We were all meant to shine, as children do. When our light shines, we liberate others.

motomadness

You know it.  I called myself running it at the last two rounds, but the bike and my confidence in the bike weren't there.  Things are definitely on a different path now.

SBK-Ike, are you coming to Gingerman this weekend?

TZDeSioux

glad you got your problem worked out. What did GP Tech do that you didn't do? What was the problem with the motor?

motomadness

Man let me tell you:
- clutch basket was bad.  Three of the rivets that hold the basket to the gear were busted and move very easily by hand.
- The one thing YOU (SD) told me to check, and I didn't - the transmission, also had problems.  The circlip that holds the shift rod in place was not in its race/groove, and a bolt holding one of the gears in place was backing out
- The deck height didn't match bank to bank, and the piston protrusion was too low.  My problem was I pretty much just rebuild to what I bought, thinking it must have been correct.  Live and learn.
- My timing and jetting were off (jetting was way off). Now my plugs are probably reading within a few main jet sizes.  I had to drop the nozzle down two size and my main down 5 sizes.  There's still more I can do, at least that's what GP Tech, LLC. says.  If only I had the money.

Now, I've got more closely matched combustion chambers, new crank, new pistons/rings, new reeds/holders, new clutch housing assembly, new clutch plates, resynched the carbs, cleaned up plugs, new brake pads, new ss-braided front brake lines, rebuilt front master cylinder, bead blasted rotors, new grips and a fresh set of Bridgestones.

=

better handling, accelerating and stopping gp bike.

It's not an '03, but I am still looking forward to challenging you for the lead in a race some time in the near future I hope.  

In conclusion, I think I have a better baseline to work off of, what tools I still need to buy and I am more familiar with two-stroke diagnosis/repair.  The only thing I haven't taken apart is my suspension

TZDeSioux

Sean..
holy moly. Sounds like big $$$. I can't believe homeboy sold you a bike in that condition without telling you the problems. The clutch basket has a habit of backing itself out and you have to use a 10 ton press or some crap like that to press it back on. If it happens again, I recommend you buy a billet basket. So now that GP Tech built your motor for you.. you going to know what to do in the future? Did they provide you with notes so you know the specs in which to build the motor? A happy TZ is a TZ that's had all it's consumables replaced on schedule everytime. To me.. it's not worth the headache of trying to push parts past it's limit. Take your motor apart often and measure and measure some more :) I already took my motor apart and replaced a few key top end items even though it's not at the limit just because. By the way, what did they set your deck height to? on my 98.. I always ran ..01 positive. The 03 is .04 negative. I'm going to play around with the new bike and set the height to .03 positive, advance the timing to 2.6 BTDC and see if I can get some more mid range grunt out of it. It'll probably make the bike a bit easier to manage. I'm also going to order a set of heads and send it out to MCE and have them cut the heads to 8.1cc so I can get the most out of the leaded fuel.

motomadness

Yes, GP Tech gave me an entire setup sheet for my engine.  Now I have to buy a deck height gauge or bracket to use the gauges I already have.
I believe before I was way too negative, now I am definitely on the positive side.  They advanced my timing to 1.85mm.  That along with the other changes definitely gave me a new bike.

As far as buying a crappy bike, I'll know what to look for the next time I buy a bike.

Here's a question for you:  how often do you change your clutch plates?

I have also decided to add the GTU to my race schedule.  Now I will be racing GTU, MWGP and LWGP.

TZDeSioux

I change my clutch plates about every 3 race weekends depending on how bad I fry them on race starts. I usually take them off and clean it after every race weekend. At that time I measure the plates for thickness and check the steels to see if they are warped. I throw away the warped ones and wet sand the good ones and put it back into use. This past Road America was terrible on my clutch. Slipping the clutch for a mile on the start with the super tall gearing killed them.

1.85 BTDC.. hmm.. isn't stock 1.5 on your year? Did they tell you to run any specific octane fuel to avoid detonation?
I want to run GTU also but I can do without the additional wear and tear on the bike. I'm thinking about ULGP at Gingerman and maybe blackhawk depending if I can make the bike a bit more user friendly  ;)

motomadness

Stock is 1.5.  He used to have a 1994 so I trusted his judgement.  I told him what fuel I used, but I don't recall him making any rec.'s on octane levels.

Thanks for the advice on the clutches.