Going to the track

[EMS]

This one is my favorite. A few years ago, during a Winter Meet in Columbus, visiting Geoff Smale had brought a video of an on-board sidecar lap at the Isle of Man TT. He could not leave a copy.
This one is the same thing, but with a bonus: John Holden takes you through the whole thing with a detailed commentary of the track

https://www.youtube.com/watch?v=IKYAv4tFVZw

[jkotsi]

That is a great ride around the Isle. How many laps before you can do it in your head?

[jkotsi]

A quick update on the frame build direction.

I had emailed Roland Skate, he replied with some pics of his bare frames let me know the difference and how they got to where there are. He is interested in the Gixxer swingarm and asked to let him know how it turns out.

AHRMA replied regarding the mods and I talked with Thad Wolff. How lucky can I get! Since he raced Tom Marquardt's CBX at Barber I asked what he would change to improve the bike "the seat, its too low". The rest of the bike is solid and wouldn't change anything.

A quick call to Tom Marquardt turned into a longer conversation. Discussed how you go from a stock Pro Link to a race ready frame, there is more than you can see in pics. He said he would try to mail off build drawings and notes from his builds. Incredible!

Last call was to Denis Curtis to set a time to drop the bike off for a little nip and tuck.


The outcome, build for 24-1/2 degrees rake with the ability to adjust plus or minus 1 degree, trail should be no more than 100mm and raise the engine while keeping the counter sprocket, pivot and axel in line at mid point of travel. Swingarm drop should be close to 13 degrees as a starting point with the bike unweighted.

Use the Pro Link arm with Ohlins S36P, CBR F2 forks in CB900 triple clamps, F2's if the trail is too low.


Looking for a loner set of engine cases in Jan to ease the work in the frame jig, Toronto area if there are any sitting around.

[NobleHops]

So awesome, priceless intel from Dr. Tom!

I found the same thing during my short but earnest career as a roadracer - a guy that might enjoy having your windpipe in his teeth on the track would disassemble his bike to loan you a part so you could make your race. We experienced that (in both directions) many times. A real racer wants to race you at 100% of your capability.

Please do keep this thread updated, this is great stuff.

[daves79x]

Sounds like you are talking directly with the best! I have a set of cases you could use, if you could find your way to Erie, PA. I can tell you from a spectator's view, there is nothing wrong with Dr. Tom's bike or Thad's riding skills. Except for a cooling issue, he'd have been right there in both races at Barber.

Dave

[jkotsi]

Cooling has been an issue for Dr Tom's bike, he said he would make some changes over the winter.
Flip the front cooler to feed oil through the top and possibly relocate the under seat cooler. He has lost a few cranks due to oil problems. Runs with a temp and pressure gauge.

Thad had the temp up over 320 degrees with pressure at 30psi while racing, right at the limits.

I had read that Roland upgraded the oil pump in the Beast, I didn't know this was possible, with the CB900's the pressure relief valve gets shimmed. Is there a mod to increase the oil pressure in the CBX?


Dave, thanks for the offer of the cases, Denis is waiting to hear back from someone local, if that doesn't work out I may be making a drive south.


Cheers Jim

[EMS]

Looks like you are getting the best advice there is from the right guys.
I thought I heard that the temperature problems on the bike were caused by the wrong connection and a reversed oil flow?
Shimming the pressure relief (spring) on an oil pump is a common way to increase oil pressure on a pump. I don't know if that's the way to do it on a CBX. Never done it myself.

[EMS]

Here is a picture of Dr Tom's bike. Don't know if it shows a current status, but you can see, the frame mods in the area of the top engine hangers.

[jkotsi]

I like the welded upper front engine hanger, very little chance of flex, maybe more work to pull the engine. Hard to see in that pic but the rear mounts were raised as well.

Look at the line through the counter sprocket, pivot and axel, almost straight with the wheel suspended. I would have thought the rear squat would increase and make corner exit wide. Not the case, mid corner and exit are good with Dr Tom's set up.

The other things to consider in changing the frame is to get a 50/50 weight distribution and the counter sprocket as close to the swingarm as possible.

Thinking the engine could pivot at the lower rear engine mount and shorten the wheel base. I'll try and weigh the current set up and see approximately how far the front wheel needs to move back.

[EMS]

Can't really tell if the rear hangers were raised at the time these pics were taken (2007)
Here is a fuzzy close-up of that area from a different pic and they seem to be in the stock position

[jkotsi]

The rear mount is only moved a small amount maybe 1/2". I couldn't see it in the pics below but it was complete then.

Courtesy of CBXtacy
viewtopic.php?f=6&t=3512

[steve murdoch icoa #5322]

Jim, you sure do have the right guys feeding you info on your project.
I have a bottom end of a '79 here but unfortunately it still has the studs, clutch and transmission in it. If you get desperate.

[jkotsi]

I have been wanting to do this for a while, weigh the bike.

Going on a diet 540lbs, 265 front and 275 rear on a bathroom scale. I weighed with in 1 lb. lighter on a digital scale in the house. Includes 3/4 tank of gas.

I can reduce the total weight but I like the split, 49/51 front/rear distribution.

[jkotsi]

I wasn't going to get into engine building this season but I have bought a 1979 intake cam.

The valve seals, intake cam and a slotted sprocket will be degreeded. The CB's work with a split overlap, assume the same here basically add 5 degrees to intake from stock.

The question I have relates to using the Pipe Max program for header design. I will try and post a screen pic. What would a good estimate of the volumemetric efficiency be for a stock 79 engine?

[EMS]

What would a good estimate of the volumemetric efficiency be for a stock 79 engine?

That is quite a question. I am not sure whether this is something you should burden yourself with in the pursuit of your goals. We all know that the CBX was not an outstanding example of engine engineering as far as load change is concerned. The inlet tract has a lot of shortfalls, mainly because of the width of the carburetor bank that made the engineers angle the outer ends inward in order to provide knee clearance for the rider.
Over the years, tuners have tried to improve upon this by machining and reconstructing the inlets in the cylinder head.
Considering the limitations for a naturally aspirated engine, my guess is that the stock CBX's VE is at the lower end of the range, maybe 65-70%.
Without doing some work on a flow bench, it is hard to say.