500cc, two stroke single test/build.

Sunday I pulled out my old WR430 Husky. What a blast! I seldom ride dirt anymore but Braaap, Whoo-Hoo!

 

I finally bought the bottom end parts for my 500 single. Since the parts came from England, I thought I should proceed while the GBP is down. I have to build it now since I just spent more on these few parts than I paid for the bike.

Funny that Coupe and I are moving on our stuff at the same time.

 

I'm back working on this project. I'm going to put it together initially with a husky 430 engine instead of the 500. Less hp but I know it doesn't vibrate too bad. I think I can have it on the track soon but it will not be well developed when I first bring it out.

 

Me Too..could it be a Covid side effect.? But I've had these symptoms for years

 

I'm finally back on this project. Bare in mind this is just a test to see if the bike is good enough to finish a build as a road racer. Like I had mentioned earlier, I am going to put my mid 80's 430 Husqvarna motor in it for now instead of the 500 motor. This bike is for V6LW.

This original bike has over 12 inches of travel at each end. I want to lower it so I will shorten the travel. I successfully (I think) shortened the travel on the stock Ohlins shock myself. After Googling all the "experts" and reading some reputable suspension shop people sites, it appears the first step is to just put in a spacer in the shock so the bottom position is maintained but the stroke is decreased. I successfully came up with a way to safely remove the spring then had to make my own "pin spanner" for one on the shock features. After doing some careful layout and measuring, I determined a 1.5 inch spacer would change the wheel stroke from 12.5 to about 8 inches. I did this and the shock still works well and the adjusters still work. Since I have owned and raced several Husqvarnas through the years I went to look for a used shock spring to shorten. Amazingly I had two factory made shorter springs so I put one on the shock and put the shock back on the bike. The rear of the bike sits several inches shorter and feels pretty good. I will be fiddling with pressure, preload, compression and extension settings.

I am now preparing to put SV650 forks, wheel and brakes on it. Then I will finalize ride height and ensure I have cornering clearance. If there is interest, I will throw up a picture when I get the forks on it.

 

Definitely post them up. I need to get back on mine. I need to do the same with my rear shock. I mocked a Penske up that I had for an SV, but now that I have another SV. It needs to go on it. I'm considering finding a longer front end than the GSXR I have on mine. Its really too short. I could use another 1.5 to 2". I have a SV front and will check it out. I have also considered checking the geometry that would happen if I shortened the factory forks even though they have offset lowers.

 

I was surprised how easy it was to restrict the stroke of a rear shock. Of course it may not work when tested.

The SV front end I'm putting on mine may be too short also. I may know this week end. If so I am planning on modifying or making new a top triple clamp. Another possibility is making fork tube extensions. I have some fabrication abilities but I can also draw things up and have them made.

 

I considered doing that with the GSXR forks. I would have to extend the adjustment needle for rebound in the cartridge but it wouldn't be a big deal. At that portion it just an aluminum rod. I know fork extensions are common on some modern sport bikes, but I was always a little concerned of putting any moment load (not an axial torque but more a shear type load) into a tall cap which would be aluminum. But with support from both triples, its probably a negligible amount.

 

I agree. If I go the extension route the pieces will go over and clamp around the fork tube. The top of the extension would slip into the top triple clamp and be clamped.

I am not recommending this to anybody but a free body diagram of a fork tube for "simple" forces puts more force on the bottom clap as opposed to the top clamp when just considering moment loads from something like braking. I would not mess with the bottom clamp.

 

I think extension are really popular on Hayabusa forks. and I believe its common on GSXR forks as well. So I'm sure its fine. Its just something that mentally messes with me. Post up what you come up with in terms of trail and rake angles.

 

This is the suspension so far. The rear is set up with 8 inches of travel. The front is the SV650 forks with about 5 inches of travel. The front fork tubes are just below the top triple clamps. I plan on raising the front even more as if it had three inch longer fork tubes. Then I will measure rake trail and maybe others things. Later I will make fork extensions as needed.

In this configuration you see the bike leaned over at 50 degrees. There is still a little peg clearance. Of course I have to look at it as if the suspension is somewhat compressed and it has the correct wheels/tires. Obviously there is more adjustments and changes to go but at least I am getting the stuff to fit.

 

It will be interesting to see it once you get the rear wheel on and a front tire on. That was when things started to really look like a road race on mine. Good progress! Any idea when you plan to bring it to the track. Maybe I can try to get my Husky ready and we can ride the crash truck back together.

 

As long as we're in the truck and not the bus!

 

Last night I measured the rake and trail. I did this after I set the heights as if it was on the correct tires and rims. I was quite surprised to find that the rake and trail are likely too much. The rake is 29 degrees and the trail is 5.5 inches. Compared to sport bikes these are both too much. Instead of fork extensions I need to slide the fork tubes further up to lessen the rake and trail. I will modify the upper triple clamp so I can do this. Since this bike is very light it can also likely tolerate higher rake and trail which slows steering and increases stability. Still 29 and 5.5 is too much even compared to the Husqvarna desert racers.

I could increase the rear stroke but the 8 inches I have it set at is more than enough. If by raising the fork tubes (which I am going to do) it makes it drag the pegs I can modify the top shock mount to raise the rear. This would further decrease the rake and trail.

This is fun and I sure hope it works. After the suspension work the bike will just take reassembly to run it up and down my driveway.

 

What kind of swingarm angle do you have?

 

I've got it all back apart now but I will check when I put it back together.

With the restricted rear stroke, I am sure it is quite different than stock.

Any suggestions?

 

I know typically, with a super single, you will end up with a very flat swing arm angle. I have been told by multiple people who have raced and built 450gp machines, this is completely normal and don't stress it. As long as you have a few degrees, it will be fine. btw I found that tire. I'll shoot you a text.

 

Excellent!

 

I have the forks set up and the engine set in. It is the 430 engine not the 500. Making progress.

I expect to get and mount tires soon then mess with geometry more. I probably will raise the rear.

 

I'm in a bar drinking a Guinness doing nothing so what the heck I'll blab about this project.

I stiffened up the back and I think it has enough lean angle to ride. The front end is working out. Since the forks are closer together than as if they were on the sv650, I had to drop down to one disk and remount the caliper but it is working out. The 430 engine and its expansion chamber bolted right in to where the 500 came out. I have a good 120 17 dunlop to put on the front. The rear will probably be an 18 inch DOT of some kind. There won't be any bodywork at first. Just a dirt bike with number plates. I'm getting excited to try this thing out.

V6LW at Road Atlanta 5/27 I hope.