GT750 Drag Bike

rngdng · Post by **rngdng** » Wed May 20, 2009 4:41 am

I agree that carbs are still suspect. The passages in there are really small and hard to get perfect.

Lane

water cooled · Post by **water cooled** » Wed May 20, 2009 8:41 am

Cleaned all three carbs this morning (thoroughly). Though it appeared that 2 out of the 3 carbs may have had blockage in the slow jet, same issue persists with the RH cylinder with no combustion at idle but that condition changes above 2k. The only thing I can think of is that the ignition trigger has moved and the timing on the RH cylinder is just outside of the range for combustion at idle. I'll re-set the static timing of the RH trigger later today and try again.

water cooled · Post by **water cooled** » Wed May 20, 2009 9:32 am

Checked timing of the triggers...

RH cyl: 0.142 BTDC (24 deg)
C cyl: 0.136 BTDC
LH cyl: 0.143 BTDC

All three plugs are wet but not fowled. Cleaned and re-gapped to .76mm. Tested for a solid spark on all three plugs.

I'm going to switch the RH and C carbs with each other and see if the problem moves with the carb. Otherwise...I'll run a compression test on the RH cylinder...after that, I'm out of ideas...

water cooled · Post by **water cooled** » Wed May 20, 2009 10:01 am

Problem went away when I switched the carbs...switched them back and still no problem.

I haven't synchronized the carbs yet but I have done what I could to make each carb setting as identical as possible from the cables to the air screw...

I suspect, that is my next step. Unfortunately, I dont know what the cause of the faulty RH cylinder at idle was.

tz375 · Post by **tz375** » Wed May 20, 2009 2:40 pm

Maybe something as simple as a slight air leak or maybe the slide not opening as fast as the others.

for really sharp pick up the way to synch carbs is using a piece of stiff wire in each carb mouth under the slide. As you open the throttle they droop.

It is so easy to see the differences form one to another.

Suzukidave · Post by **Suzukidave** » Wed May 20, 2009 4:17 pm

tz375 wrote:Maybe something as simple as a slight air leak or maybe the slide not opening as fast as the others.

for really sharp pick up the way to synch carbs is using a piece of stiff wire in each carb mouth under the slide. As you open the throttle they droop.

It is so easy to see the differences form one to another.

I dont want to make a duh comment but Richards tip is while the engine isnt running

tz375 · Post by **tz375** » Wed May 20, 2009 6:00 pm

Good point Dave.

water cooled · Post by **water cooled** » Thu May 21, 2009 4:22 am

Richard, thats a great idea and easy way to check. Dave, yours is even better!!! I wished I read it before I tried Richards idea.

I have to get the air shift cylinder mounting stud welded up today or tomorrow and get that system completed...then some final machining on the rear caliper hanger and banjo bolt. Seems the stock bolts are too long and bottom out inside the Grimeca caliper. It looks like I can cut one down to fit.

water cooled · Post by **water cooled** » Thu May 28, 2009 8:04 am

Yesterday, I finished the component installation and routing on the MRE air shifter...pumped up the system and tested. The cylinder is not attached and needs a pivot pin welded to the frame and a shift arm added to the foot shift lever.

The system is supposed to hold pressure within 5 psi for at least 1/2 hour so I have a very tiny leak somewhere that needs to be chased. Next, I'll tie the "air-kill" switch into the MSD ignition and test the bike through the gears while running to help ensure the system is working properly.

Starting to focus back over to the front and rear brakes to finish them off completely and then need to fab a torque link arm for the rear caliper hanger.

more later...

water cooled · Post by **water cooled** » Thu Jun 04, 2009 10:01 am

Here are the last couple pictures I can post before the AMA race next weekend in Martin MI.

I completed a number of changes since the Norwalk race in October. Some, for hp improvement...some for lightening up the bike and some to gain better access to components at the track.

Finally finished the alignment and fitup of the rear brake hanger arm and torque arm, chain and rear master cylinder. Corrected a tiny leak in the MRE system and tested...held 110 psi for more than 8 hrs with no perceptable pressure drop. Wired the MRE system into the MSD ignition. Finished the tail-light installation and bled the front and rear brakes.

MRE air cylinder will get welded on early next week and will get a final test. Waiting for a part to arrive to finish the exhaust install. Scheduled a dyno test for mid-week...leaving Thursday night for MI.

This is about the best I could do for now...just cleaning up lots of little things and starting to pack everything up to go. The bike will get a decent paint job sometime during the summer once I feel that there will be no more welding to the frame. In between races, I have additional modifications planned for the engine and parts are arriving for that already. No rest before the Indy race in August to get those mods done...all leading up to the October race in Norwalk where I have much higher expectations for the look of the bike as well as the ground-shattering, asphalt buckling performance.

jaybob · Post by **jaybob** » Thu Jun 04, 2009 10:07 am

Oh Yeah Dyno run. Now you are talking. Looking good Kevin.

Suzukidave · Post by **Suzukidave** » Thu Jun 04, 2009 8:30 pm

Its looking lean n mean Kevin

tz375 · Post by **tz375** » Thu Jun 04, 2009 9:50 pm

kevion,

That's looking mean. Well done.

BTW, what is the tail light for? Is it a "stock" type class or a safety thing?

water cooled · Post by **water cooled** » Fri Jun 05, 2009 5:04 am

Thanks Dave and Richard.....

The requirement for a tail light falls under the General Regulations 2.8.6: All entries must have a functional tail light attached to the motorcycle during night operations.

At Test and Tune, I made my first pass at 10pm though qualifying and finals dont seem to be scheduled into the evening.

The class I am in is EE/HH M which is 740-779cc/Heavy Hitter 200+) Modified.

The "Modified" is the next class after Stock. It allows for lightly modified frames using stock engine cradle. It allows for struts, wheelie bars and slicks as well as an extended swingarm but must use the stock pivot. Front foot pegs must be within 6" of stock location.

My wheelie bars will not be ready for Martin but I expect to have them done and mounted for Indy.

tz375 · Post by **tz375** » Fri Jun 05, 2009 6:32 am

Thanks Kevin.

200+ class. We had better find you a whole lot more HP. Is partial streamlining allowed in that class. And at 200per, aerodynamics count.

Are you restricted to Gas in that class or could you use methanol? Alky is worth 10-15% with jetting changes and can stand compression ratios up to silly numbers.

Now where id I put those 44mm Lectrons and that lockup clutch?