XV920 EFI Turbo.... Done (mostly)

[turbodog]

My prior posts on this bike are probably misplaced in the Cafe section, so will continue here.
My turbo plans depend completely on the success of my 'upside down' rear suspension:

So, I figure I should prove that out before going too much further. When the temps here hit 105 and the original XV forks started leaking preload air, I figured the time was right.

So, on went the 2002 GSXR750 trees, forks and calipers; CBR600F2 wheel; Thruxton-spec aftermarket rotors. Subtle changes to the front and rear motor mounts bring the rake and steering stem height much closer to GSXR specs than the original XV.

And on went my CBR600F4/Buell/homebrew suspension:

Sprocket alignment is perfect, time to button up the engine and put the wiring harness back on.

In this heat, and with work, I'm guessing 3 weeks to the 1st test ride (still carburated and normally aspirated)

 

[turbodog]

Re: XV920 New suspension

Lots of hours on fiddly stuff, like tucking all the rear disc brake master cyl hardware behind the footpeg bracket:

I stuck the bodywork on temporarily to see if the new rake angle of the frame on the motor was apparent:
was

is now

Yes, I'd say it is apparent...!

 

[turbodog]

Re: XV920 New suspension

She went aroung the block a few times today. The rear suspension did fine, but I'm gonna have to make a new front header pipe. The tire just kisses it when braking hard. It deflects the rear of the tire to the left, making the bike want to step out from under me. A few pics (before the ride, just in case I came back with some road rash...):

 

[silentfurymm]

Re: XV920 New suspension

More info on adjusting the motor mounts to achieve new steering rake? Did you make new mounts?

 

[turbodog]

Re: XV920 New suspension

The front mount is a XV1100 (late model). When combined with a 1st gen frame, it brings the steering head down about 2 inches. It does require welding on an extension to reach the 2nd frame mounting holes. The rear has 1/2 inch spacer added to the rear cylinder mounts. This steepens the rake. The location of the added hole in the front mount is determined AFTER the rake is established by the rear mount. I would go less that 1/2 rise in the rear if I do it again. The front tire to header clearance is a little tight. I'd go with 3/8".

 

[Swagger]

Re: XV920 New suspension

How did you come up with the motormount swap good sir? I ask because I am seriously considering stealing the idea but, credit where it's due....I want to attribute it correctly in the blog. I'm working on my fixture now (layout) to fab and weld up a trellis style upper frame/seat base combo this winter but in the meantime I'm REALLY intrigued. I looked really seriously at cutting the steering tube off and rewelding it lower on the framehorn but just can't convince myself it can be done cleanly or solidly enough so this is maybe a good intermediate step.

Also, in the time you've been running "Koched" have you noticed any problems with stress on the engine without the center joint in the frame? The only thing I would want to fix would be the tire/headpipe clearance and maybe a wee bit more ground clearance as the sump looks pretty low for a sporting machine. Thoughts?

 

[turbodog]

Re: XV920 New suspension

I can take full credit for the front motormount idea. I realized it while holding 1st gen and late-model front mounts side-by-side. I knew there was a good reason I never get rid of old parts, even when I buy them by mistake (the late model mount).

I tried cutting a steering stem off to reweld it lower. Result: scrap metal. There are numerous internal braces connecting to the steering tube that can only be properly attached if one is assembling the frame in the same sequence as at the factory. I kept the tube, since I have a title for that VIN, but doubt I will ever use it.

I have absolutely no complaints about the Koched frame. I was openly critical of it on Viragotech Forum at first, but have had to eat my words. I am sure it is not as rigid as a modern sportbike frame, but the tires, brakes, spindly forks and other early-80's era design and material limitations prevent one from finding the limits imposed by the frame. 3+ years and about 8000 miles (no, I'm not a long distance rider) says it is OK by me. Now, with modern wheels, radial tires, etc,etc... you might find the frame a limitation.

Nonetheless, I still like my current design better, in terms of resolving all the rear suspension forces in the main engine case, rather than via the rear cylinder (although no one seems to question Yamaha's decision to resolve all the FRONT suspension forces thru the front cylinder...).

As for cornering clearance.... yeah. That's the rub. With the GSXR forks close to max preload, and the Buell shock at 3/4 max preload, the exhaust still comes down hard in right hand cornering, under certain conditions (on the throttle, or a mid-corner bump). Sump and left side are OK, no issues. I can only imagine what folks get when they bolt a modern front end on, with absolutely NO effort to offset the lost ground clearance (Classified, etc). Photo models, not usable motorcycles. Now I know why many of Koch's bikes have high-mounted exhaust headers: http://tr1.de/pictures/gallery/sepp_koch/sepp_3a.jpg. I am already planning my next pass at a custom frame to overcome the clearance limitations.

I only have about 60 miles on mine after the suspension work, and hope to dial it in a little more. It IS very rideable. There is a test port bung in the collector... when it is ground off, I hope to feel an improvement ;D. The header wrap on the collector is already trashed from ground contact, oh well.

Hope that helps with your decision-making process.

 

[Swagger]

Re: XV920 New suspension

Hmm....might be best to run the Showa 41mms I have for now and wait on the USD swap till I get a new upper made.

 

[turbodog]

Re: XV920 New suspension

Food for thought:
Suzuki Marauder forks are longer, and still inverted type. The bike is single disk, but both forks have caliper mounts. I don't know if GSXR internals can be used; the Marauder forks do lack the adjustability of the GSXR forks.

 

[Swagger]

Re: XV920 New suspension

I'd heard that those forks would work.

I have Ohlins from a track only TLR slated for the front and a CBR600rr (no top mount) swingarm for out back.
The 41mm Showas are from an earlier GSXR750 and they are exactly 1" shorter than the OE spaghetti forks, and with the new shock I have for the rear it'll keep the clearance pretty well til lI completely redo the chassis.

 

[damarble]

Re: XV920 New suspension

Body work looks so weird floating like that. Nice work on the suspension.

 

[turbodog]

Re: XV920 New suspension

Thanks. Have over 200 mi on it, and I'm liking it. It soaks up bumps that rattled my teeth with the original suspension. Turn-in is quick and effortless. Brakes are not in the same universe as the originals. Have done the work commute 2 days now, riding my usual style, and only touched down the exhaust header once.

 

[damarble]

Re: XV920 New suspension

Even better when it works better than before. It would be nice to get that header sorted, I have concerns in that vien with my new USD front, it's looking tight, to the point where I'm considering chopping off the headstock and adding a degree or 2 more rake.

 

[beachcomber]

Re: XV920 New suspension

Even better when it works better than before. It would be nice to get that header sorted, I have concerns in that vien with my new USD front, it's looking tight, to the point where I'm considering chopping off the headstock and adding a degree or 2 more rake.

Maybe the increase in rake will affect whatever ride style you are aiming for.

If you are going to chop off the headstock anyway - why not just move it forward by the relevant amount - keeping the same rake that you originally designed ?

 

[damarble]

Re: XV920 New suspension

Not a terrible idea, I'll have to think about that if I do it. My main thinking about increasing rake is the USD front has the axle center but my stock forks were leading axle, pushing the centerline out about 1.5" more.

I should have built my own girder and had exactly what I wanted...

 

[turbodog]

Re: XV920 New suspension

We may not be talking about the same problem. My issue is that the collector, under the right footpeg, grounds in right turns under some conditions. I did re-route the front header slightly to eliminate interference with the front tire at full compression (braking dive); that's no longer a problem.

 

[turbodog]

Re: XV920 New suspension

Swagger, a few more items you will encounter if you do the front motor mount swap:
- No room for the coils in the original location. I mounted them under the frame just in front of the rear cyl and just behind the front cyl.... might not work if running the stock carb setup.

- No room for a oil cooler at the front cyl head location. That one hurts, since I had planned a cooler in that spot, dedicated to the oil going to the heads and turbo. Still pondering a plan "B".

 

[damarble]

Re: XV920 New suspension

Ah yes, different problem I guess. Not much you can do about that but move the collector or live with it.

 

[Swagger]

Re: XV920 New suspension

Swagger, a few more items you will encounter if you do the front motor mount swap:
- No room for the coils in the original location. I mounted them under the frame just in front of the rear cyl and just behind the front cyl.... might not work if running the stock carb setup.

- No room for a oil cooler at the front cyl head location. That one hurts, since I had planned a cooler in that spot, dedicated to the oil going to the heads and turbo. Still pondering a plan "B".

I was looking at that area yesterday and thinking what to do. As for the oil cooler, I've been thinking of hanging mine under the headlight..

 

[turbodog]

Re: XV920 New suspension

I just looked at the swingarm you chose. Very cool. It sure resolves the rear suspension forces neatly. I'm curious what you have planned for the rear exhaust routing. Except for that potential issue, I think I'd go that route for my NA daily driver when this rear suspension migrates to the turbo project.