GT750 Drag Bike

Suzukidave · Post by **Suzukidave** » Sun Jul 26, 2009 3:56 am

water cooled wrote:Dave,

I set all the 10mm bolts in place with the copper gasket installed and all sat flat against the head with no wahsers...so I think we are going to be ok.
\

Thats great

but it was worth checking .

water cooled · Post by **water cooled** » Thu Jul 30, 2009 2:47 pm

Here are a few pictures from today just before I load up the bike to head to Indy.

chainsaw · Post by **chainsaw** » Thu Jul 30, 2009 3:32 pm

WOW, sweeeeet looking. Great job. I hope she runs as good as it looks. How bout a couple of video clips of it going down the track?

good luck and ride safe.

water cooled · Post by **water cooled** » Thu Jul 30, 2009 4:07 pm

Thanks Chainsaw...I do too.

Well, here is a video clip...I cant tell if its purging some residual oil from the rebuild or what...it only seems to be smoking from the center cylinder which concerns me. At the last race a month ago, I had coolant that leaked into the cylinders. We drained what we could from the SIRS ports in the bottom of the crank case and flooded the crank area with oil to prevent bearing damage from the coolant. It just seems like a constant problem. Anyway, I will have to race with what I have. The crankseals have very little time on them and should be in good shape.

http://www.youtube.com/watch?v=YimTiNPv0eY

Suzukidave · Post by **Suzukidave** » Thu Jul 30, 2009 4:52 pm

Looking lean n mean Kevin and ready to walk the walk

tz375 · Post by **tz375** » Thu Jul 30, 2009 5:35 pm

Kevin,

It sounds sharper but still sounds rich. Did it start from cold without any choke or had you already warmed it up? Try one size leaner on the pilots and drop the needles one clip position and see what that is like. It should clean it up a little.

Do you have a triple EGT on the bike or a CHT gauge of some sort? need to get to a dyno to get it set up properly if at all possible. Is there one on the way to Indy by any chance or one close to eh track you could take it to? Or does anyone bring a dyno in a trailer to the AMA pro races by any chance?

We're looking for 75 -80hp in the current mild state of tune with more to come, and may need to dial it in a little closer.

Just as a frame of reference what are the carb settings now?

Tom Garcia · Post by **Tom Garcia** » Thu Jul 30, 2009 5:39 pm

Kevin - Good luck with the meet and thanks again for the Rolling Rock when I dropped by last night...

Tom

water cooled · Post by **water cooled** » Thu Jul 30, 2009 7:50 pm

The engine was cold but I had kicked it over about 4-5 times before the video started. It ran for a few seconds and I shut it off.

I tried hard to get the bike in at Crooked River before I left but couldnt get in for a test. I discussed everything we wanted to accomplish through a series of tests to dial in the fuel/air and carb jetting as well as set of static timing pulls from 24 to 21. Unfortunately, I couldnt talk my way in. At the last AMA race they did have a mobile dyno avialable. Not sure if Indy would be the same.

VM-38 snowmobile carbs
320 main
45 pilot
Q-2
6DP4 3rd down (middle clip)
3.3

The timing is much better than the last video...corrected the procedure for static timing now at 24 degree (nats ass) and retards strating at 6500 upto 9000 removing 4 degrees.

I have a Q-0 and even some P-4 sets to lean it out a bit on the low end and a set of 310s if the top needs to be leaned/.

Tom, it was my pleasure and wished you could have stayed for more than just one...but as it turns out, I will have to bring the rest of the beer with me. Darn it.

Kevin

water cooled · Post by **water cooled** » Thu Jul 30, 2009 9:52 pm

Tom,

Thanks again for the rotors and calipers...I'll start on them after I get back...huge difference in weight.

Kevin

tz375 · Post by **tz375** » Fri Jul 31, 2009 9:46 pm

Kevin,

I listened to that video a few times and it sounds like something goes flat as the revs go up and I suspect it's the retard curve kicking in. Try adding more advance all teh way through the curve. It has a nice conservative curve at the moment and it sounds like the motor is asking for more.

On a 4 stroke we'd be trying from 35 to 60 degrees of advance to get in the ball park, but on a two stroke we probably want to move at 0.5 degree increments.

At this stage I suspect you'll end up with slightly more advance than stock at low revs and stock or slightly less at teh top end - say 26 down to 22 degrees.

Suzukidave · Post by **Suzukidave** » Sat Aug 01, 2009 4:07 am

Richard , if you are going to Indy you will be seeing Kevin there

tz375 · Post by **tz375** » Sun Aug 02, 2009 11:36 pm

Dave,

That's what I did, and we had a blast. Kevin's riding just kept improving through the weekend and his luck was pretty good too.

That was a great weekend - lots of fun and nice people. Great to finally meet Kevin in person and his personal cheering squad. What a team

Pictures and video of Kevin smoking the competition coming soon. Note to self: Find out why that center cylinder still smokes so much.

Suzukidave · Post by **Suzukidave** » Mon Aug 03, 2009 7:55 am

So yall got the drag bike engine dialed and running nice

i guess the head stayed down this time ? I hope the center smoker isnt a seal its so easy to get those seals in cocked just a bit .

tz375 · Post by **tz375** » Mon Aug 03, 2009 10:54 am

The bike was running pretty good, and there's always scope for further improvement.

What really made the difference was just fine tuning to make it slightly more rideable and after that it was Kevin's riding improving from one run to the next.

water cooled · Post by **water cooled** » Mon Aug 03, 2009 12:39 pm

Hi Dave,

All indications are that the head stayed down much better this time but of course we cant be sure until the post-race tear down. Before I do that, I want to get the bike on the dyno as soon as possible.

On the smokey pipe, I want to check the float levels first and make sure the choke plungers are seating (and sealing) properly.

I've tried to look at several pictures to see if it is isolated to the center cylinder or if its the center and right...my foot or leg always seems to be blocking the view on the end of the pipe(s).