Madness or monster

[morthrane]

Did you ever see the XR650 engined RGV250 that was in Performance Bikes? (this is going back a few years).

I was SPANKED by some guy who'd built his own version with a KR1 chassis and XR650 motor...same weight, same power, but torque... I caught up with him at the Cat and Fiddle, great bike for that road.

He said it was a breeze to build, tons of space for the motor.

Bah, just find me a Spondon chassis with TZ250 running gear that fits one of those yamaha xt/srx600 motors... that would be the most pimpin' crazy fun street ride evar

 

[christofu]

Thanks to some debugging over the phone from Chris Van Andel, and push, push, PUSH from Jenna, we started up the bike for the first time today, just for a second to see if it ran.

After much futile kicking and pushing, Chris thought it must be the cam timing being out. So I pulled out the engine to
take a look and sure enough, the cam chain was off by one tooth (after I'd already checked it twice before... duuuh).

A bit more pushing (accompanied by some very promising pops) and the engine roared to life (with Jenna onboard and me running alongside). It sounds SWEET!

Anyway, we had to shut it off immediately because I want to break it in properly AND because I accidently snapped two head cover bolts and now am waiting for replacements. I mean, it was good enough to fire up with but I didn't want to run it without them (also the oil seeping out was enough to stop me

Yay!

 

[christofu]

Christofu,
I was looking at the pics and the bike looks really neat. Super light and should perform pretty hot! Who built the exhaust? It looks like 1 5/8" dia and about 44-48" from the head to the muffler flange. This seems pretty long for an engine that will rev like the Honda will?


Swiss

The main problem on the exhaust length is getting out somewhere. The bike is TINY, so some thought had to go into figuring out where the pipe could be routed and not adversely impact ground clearance. This routing ended up being the best compromise. The can is the tiniest can we could find that would fit.

Also, the CRF450 engine (or, CRF500 as mine is now) actually drops off power pretty steeply after 8500 rpm. So although it will rev much higher, it's pointless going past about 8500.

 

[christofu]

Re: Re: Madness or monster

So, wait - you weigh 102 lb

Well, I WISH I was 102 lb. No, the BIKE weights 190 lbs, I weigh 46% of the bike+rider package, so therefore I must weigh 162 lbs (in leathers, helmet, etc!)

Hey, what's the math you used for figuring hp/weight? I have a YSR I am putting a 125 motor into, and I want to figure out how much weight I need to lose to make the bike faster (using weasel Jim's math...)

I just worked out pounds per horsepower (as a check against various other bikes). So just take the weight and divide by the horsepower. A simplistic view of the world, but then that describes me perfectly (simple in the head).

 

[christofu]

Any problems with radiator fluid getting hot, with the exhaust being so close? Or did you wrap that section of the pipe?

Man, that thing looks killer

You read my mind! The first 7-8 inches of pipe now has heat wrap, just to avoid the reheating of coolant in the radiator.

 

[Swiss]

Christofu said: "The main problem on the exhaust length is getting out somewhere. The bike is TINY, so some thought had to go into figuring out where the pipe could be routed and not adversely impact ground clearance. This routing ended up being the best compromise. The can is the tiniest can we could find that would fit.... Also, the CRF450 engine (or, CRF500 as mine is now) actually drops off power pretty steeply after 8500 rpm. So although it will rev much higher, it's pointless going past about 8500."

So, is the diameter 1 5/8"? Fit is always a problem when working with custom systems, and with something this small it is even harder. The idea of the CRF dropping off after 8,500 rpms isn't hard to figure out when the exhaust system is basically tuned for around half of that. So you took the engine out to 500cc? What is your bore and stroke now? I can suggest some pipe dimensions if you would like to try to build something better? It won't be the easiest to fit, but it will perform stronger than what you have.

Swiss
Not trying to be critical, just trying to help.

 

[christofu]

So, is the diameter 1 5/8"? Fit is always a problem when working with custom systems, and with something this small it is even harder. The idea of the CRF dropping off after 8,500 rpms isn't hard to figure out when the exhaust system is basically tuned for around half of that. So you took the engine out to 500cc? What is your bore and stroke now? I can suggest some pipe dimensions if you would like to try to build something better? It won't be the easiest to fit, but it will perform stronger than what you have.

Hey Swiss,

I'm always interested in hearing new ideas! The pipe is 1 5/8", which also closely matches the exhaust outlet on the engine.

The bore is now 101mm, stroke 62mm, compression 12.5:1.

Chris.

 

[Swiss]

Chris,
For peak power at about 8500 rpms, you should be running a 22" long head pipe with a 20" long megaphone, then a connector tube to your muffler which can pretty much stay where it is. Of course, the head pipe should be 2" dia. and the meg. should be 5" max dia. but you can do it with a 4" meg for a slightly weaker "hit". Connecting tube between the reverse cone and the muffler should be at least 2" od and can be 2 1/4".
At the head, you can set up an A-R cone with flat sides to accomodate your mounting studs. The cone will have a short inner tube at 1 3/4" od and an od of 2 1/2". If you aren't familiar with A-R systems, I can send you pics of what one similar to what you would need would look like.
Note, that this system is 42" long and would probably be shorter than your current headpipe. You never did say how long the primary pipe is.
Yes, you will have to move your radiator forward just a touch! <grin>

Swiss

For all out performance, you COULD go farther than this, but I suspect that this will be hard enough for you to fit.

 

[christofu]

Hey Swiss,

Thanks for the info! The pipe is currently 41", so 42" wouldn't be a problem. What WOULD be a problem is moving the radiator forward... we're already at the limit of front wheel clearance.

To accomplish the A/R cone we'd have to relocate the radiator to the rear of the bike (under the tail section) and have an exotic network of ducts to induce flow.

So... hmmm... perhaps I should hold off on the exhaust mods until I've got all the other stuff sorted out...?

Thanks for the info!

 

[Swiss]

One idea MIGHT be to pivot the right side forward and the left back just a bit. Like I said, fitting it is always tough.

Swiss

 

[Joebar4000]

Heya!

Christophu, I have the pics from the day at the dyno - didn't want to 'steal your thunder' so lemme send them to you! Will PM too...

 

[christofu]

Ian, post away! I'm especially curious about the mini-AVIs

 

[christofu]

Update:

Well, as Ian pointed out, the beasty went onto the Dyno on Friday (while Ian was busy taking spy shots) at G-Force in Santa Clara. By the way, if you need anyone to work on your bike (anything from performing a scheduled service to building out your engine to the max) then G-Force is the right place to take your bike! The guys there are friendly, cost effective and they totally know their shit.

Anyway, putting the bike on the dyno was funny. It's a single all right. The thing vibrated so much I thought I was going to have to pay Mike's dental bill to have his fillings replaced . Also, every single bolt or screw that hadn't been wired or loctited fell off at some point (fortunately, all the important ones HAD been wired or loctited).

All that being said, the bike peaked out at 52.5 hp -- very respectable since it hasn't been tuned at ALL yet! Unfortunately I don't recall the torque numbers, but the torque curve was just incredible... the most impressively scarey torque curve I've ever seen.

Right now the bike peaks too low, about 7500-8000 rpm. Mike, looking at the charts with an expert eye suspected that it was because with the big bore 500cc kit in there the intake bore through the carb, engine and valves wasn't big enough to draw in the charge at higher rpms without the intake charge going hypersonic .

This was proved out when we fitting a velocity stack from a GSXR-1000 to the carb... with the increased speed of the intake charge the engine dropped off much sooner (about 6000 rpm). I didn't know this but apparently it's bad if the intke charge goes faster than about 0.6 mach. Who'd of thought? Hypersonic sounds so much cooler .

Anyway, so Mike is currently working away with his single cylinder engine simulation software to figure out the optimal changes to the engine and carb to let the engine rev out to about 9,500 (and based on the curve we were looking at at, about 58-59 hp) before it drops off.

I'm also seriously thinking about relocating the radiator to under the tail section. I continued to be worried about front wheel clearance, and it would be nice to have room to build a killer exhaust like the one that Swiss came up with for me...

 

[Joebar4000]

Heya! Thanks for the kind words about G Force

Would be real curious to see how the underseat radiator goes, if it goes...that could be cool You'll have to make a damn good rubber mount tho.

Vibration doesn't really describe the bike, I took an .avi with the camera showing the tiny bit of coolant in the catch bottle being turned into mist by the vibes!

Does anyone know where I can host the AVI's? There not desperately exciting, but might be nice as a 'diary' for the project.

In the meantime, here are a coupla pics, I was sure I took more, but apparently not...hmm...

 

[Joebar4000]

Here's a pic of how close the swingarm gets to the larger-than-stock countershaft sprocket...couldn't get a Rizzla in there...

 

[Joebar4000]

And here's just an overall pic, looks like it was originally built like that

 

[christofu]

The good news: The time it takes me to drop the engine completely out of the bike is down to 25 minutes.

The bad news: I didn't apply loctite to the bolt that holds the auto-decompressor onto the end of the cam shaft. The bolt wiggled partially free... and put a big hole in the side of the head cover. Thank god the engine is such a tight squeeze into the frame! The bolt couldn't come all the way out because it ended up hard against the frame.

Anyway, new head cover on order (another $100 for the DUH FACTOR). About a week until I get it. Sigh.

 

[Joebar4000]

The good news: The time it takes me to drop the engine completely out of the bike is down to 25 minutes.

The bad news: I didn't apply loctite to the bolt that holds the auto-decompressor onto the end of the cam shaft. The bolt wiggled partially free... and put a big hole in the side of the head cover. Thank god the engine is such a tight squeeze into the frame! The bolt couldn't come all the way out because it ended up hard against the frame.

Anyway, new head cover on order (another $100 for the DUH FACTOR). About a week until I get it. Sigh.

Poop, sorry to hear that Is it actually all the way through, because it didn't leak at all on the dyno?

Methinks you're going to need to get LOTS of tiny drill bits and get to be very good at lockwiring, and not just the usual 'to hold it on' lockwiring, the Mike Sampognaro 'to hold it TIGHT' lockwiring...

 

[christofu]

Beastlet update

OK, I've now christened the bike "The Beastlet" and as many of you know it went for its first test ride at Sears Point last Tuesday (at the Zoom Zoom day).

A few points:

• I have new leathers. New leathers and a bike this tiny do not work well together. Seriously, it look me three tries to even get my feet on the pegs. Even then (for a while) I couldn't get the balls of my feet onto the pegs. However, the leathers are breaking in (slowly) and as they break in my foot positioing is getting better!
• The current gearing (15/43) is way, way, WAY too short for the bike. Basically, I was riding around in 4th & 5th a lot and was at red line in 5th at the start of every straight. I spent a lot of the straights just motoring along. I've ordered some new sprockets from Sprocket Specialists (they're custom ones... RS125 pattern but 520 chain size) in 33, 35 and 37 teeth.
• An alternative (or in addition to) the sprocket sizing changes would be to buy a new wide ratio transmission from Baja Designs. It's $500 but makes the 3rd, 4th and 5th gears 17% taller. It also involves cracking the cases on the engine to install (no cassette-style transmission on THIS engine!), so assume another... what? $500-$600 to install? (no way I'm doing THAT by myself). What do you think?
• One of the advantages of the Baja Designs transmission is that the stock CRF450 transmission has a minor reputation as being weak for high-traction purposes like roadracing. I worry about the transmission going boom during a high-rev downshift. Thoughts?
• A potention solution is an STM slipper clutch, about $750 but I can install it myself. Thoughts?
• Finally, the carb on this baby definitely needs to be bored. The bike bogs badly as soon as you hit about 8k rpm and it's almost certainly because of the big bore 500cc cylinder not being able to draw intake fast enough through the too-small carb mouth.

The bike is so much fun to ride it should be illegal. It steers so fast it's ridiculous. At one point I almost ran off the INSIDE of turn 3 because the bike steered so fast. The bike can change lines mid turn, no problem.

With the current gearing it's funny to get on the gas. The thing accelerates like a rocket ship (but has a low top speed). You really have to hang on. I was pulling major (inadvertant) power wheelies coming out of Turn 11. Yeehaw!

 

[Joebar4000]

Re: Beastlet update

• The current gearing (15/43) is way, way, WAY too short for the bike. Basically, I was riding around in 4th & 5th a lot and was at red line in 5th at the start of every straight. I spent a lot of the straights just motoring along. I've ordered some new sprockets from Sprocket Specialists (they're custom ones... RS125 pattern but 520 chain size) in 33, 35 and 37 teeth.
• An alternative (or in addition to) the sprocket sizing changes would be to buy a new wide ratio transmission from Baja Designs. It's $500 but makes the 3rd, 4th and 5th gears 17% taller. It also involves cracking the cases on the engine to install (no cassette-style transmission on THIS engine!), so assume another... what? $500-$600 to install? (no way I'm doing THAT by myself). What do you think?
• A potention solution is an STM slipper clutch, about $750 but I can install it myself. Thoughts?
• Finally, the carb on this baby definitely needs to be bored. The bike bogs badly as soon as you hit about 8k rpm and it's almost certainly because of the big bore 500cc cylinder not being able to draw intake fast enough through the too-small carb mouth.

Heya Chris,

glad you had fun with the beastie! If you don't mind me adding my threepenny bits...

1. Gearing - change the final drive ratio before even THINKING about mucking about with the gearbox. Don't forget that as you raise (lower) the final ratio, you'll also 'space out' the stock gearing quite a lot.

2. IF you still want to do it, I think you're price is about right, whether you brought it to G Force or not.

3. Slipper clutches are always a good idea!

4. Carb boring - what size carb do you have on there? It might be cheaper (and certainly easier) to look around on EBay first...also, did you ever do the calcs on flow/intake-exhaust runner length, width etc. etc.? Or is that how you ended up on the stock bore being the biggest restrictor? I can't remember the conclusions we came to at the shop. Be nice to run the numbers by Dema Elgin before going and hacking stuff up - frequently the 'ideal math' numbers don't work in the real world and he has a lot of experience of how to 'fudge' the numbers to make them real world relevant.

5. You also need a second opinion of that riding position, let me know when you're having you next track day and I suppose I could force myself to putz it round and tell you what I think, if you twisted my arm

WHEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE!

I'd love to try to get hold of a light-weight stator for that thing and make a road bike.