Topic: Purple Rain Bill's CB750/900 Turbo 1972

[TurboD]

That's not pretty for sure.

Lets keep in mind, the primary causes of detonation is lack of fuel quality and or too much timing. I would not be quick to blame the ignition system or boost level.

A simple easy way to reduce the timing is to limit how much the advancer advances. I usually shoot for about 8-9 degrees off the total.

[MRieck]

Wow Bill, nice ashtray!  That won't buff out.  Did it tear up the liner?

Mike, Dragbike wouldn't have any say so about the track.  On top of problems I mentioned, the right lane timing light at 1000' was not operating.  This same friend said the track owner does very little maintenance.  I would guess the track personnel are not to concerned with accuracy in the timing system.  IF that is the case, it makes it very hard to dial in a vehicle.

I understand that Dave  .....I figured Dragbike may be able to make those problems more public knowledge. At that point maybe the owner tries to clean things up. Or maybe he doesn't.
 Bracket racing is all about measuring time. Somebody should get on somebody's a$$ about it.

[bwaller]

Rough luck Bill. As TurboD says we've all heard stories about inconsistent fuel quality and that's something to be mindful of. Best to remove any & all sources of bad luck inducers though!! Good luck forward.

[Bill/BentON Racing]

All ignition based problem, no retard with too much boost. 5-6 lbs would have been fine, 17-20+, not so good. We going with more cc and more boost! WTF? We going in the 9'$!!!!!! No typo error, it's going to happen! $tay  tuned!
Fuel was VP C16, not the problem. Got me a nice expensive ashtray! ! See y'all at Valdosta in the 10's for sure....both bikes!  , Bill

[BPellerine]

old school 900 pistons?sure sucks!billp

[kmb69]

Bill, Check if Mike still has these:

http://forums.sohc4.net/index.php/topic,149621.msg1722577.html#msg1722577

[TurboD]

I would like to add to my comment above.

*Lets keep in mind, the primary causes of detonation is lack of fuel quality, *lean fuel mixture* and or too much timing. I would not be quick to blame the ignition system or boost level.*

Bill A couple things to consider. The ATP intake is very small, the outer 2 cylinders often times will be leaner than the center 2. And you do not need a boost retard if you reduce and limit the timing. I have ran bikes up to 35 lbs of boost without any problems with a VERY basic ignition. The key is limiting the timing.

[MRieck]

Bill, Check if Mike still has these:

http://forums.sohc4.net/index.php/topic,149621.msg1722577.html#msg1722577

I have them.

[scottly]

Bill, please check the ring end gap on the surviving cylinders.

[Bill/BentON Racing]

Mike, I'll take em. No retard, too much boost, and too lean because of no fuel pressure to keep bowl full, old school 44mm Kehein carb. Swapping out carb, installing pump @ 4 psi. Dyna 4000, with boost retard box, 2 step, replacing log manifold ex, with the newer style 4-1 ,the separate power pulses spool up turbo quicker. Got plans for Pro ET and Super Eliminater class. Bill

[dragracer]

Bill, we'll get that Dyna 4000 hooked up and the retard box wired to pull timing. This bike is going to make some safe power the next time it comes out!!!!!!!!!!!

[TurboD]

Bill if you do not have a fuel pump on the bike, this is the problem that caused the meltdown. There is no way that a single float bowl, single needle and seat with gravity feed will keep up with anything over a few pounds of boost. A lot of pressure is not needed, 2-2.5 lbs of fuel pressure will keep up. Too much pressure and the needle and seat cannot deal with it.

Many of the changes you listed are not needed. The 44mm carb is already larger than the turbo inlet. It is unlikely that changing the exhaust will help as well, A small engine (<1100cc) will spool better keeping the exhaust size in check.

In the past with Kawasaki's we have made 280 rwhp with these old single carb setups using very basic electronics.

[Bill/BentON Racing]

D, keep info coming. Carb size is fine, not adjustable as later Bendiix Zenith ones. Of course it ran out. Why we wanted to run 5-6 lbs with std or slightly retarded timing. You really think a young gun is going be watching the gauge? Not anyone's fault but mine, I knew what would happen....did!  . Exhaust not bigger, different design from Bill Hahn ,the creator. He probably knew what he was doing.  .  I'm going to keep it as simple as I can. Keep up with the input, I appreciate it!  Bill

[NalleyRacing]

Ah, I really can't wait to ride this purple rocket again!

[dragracer]

Ah, I really can't wait to ride this purple rocket again!

We're going to keep you off the straight away over 1/4 mile though. Lol.

[Bill/BentON Racing]

Yeh, that test ride was a little long!!! My bad again,  wasn't specific enough! We'll get it though, stay tuned, Bill

[Bill/BentON Racing]

Trey's first pass is on YouTube. Under Trey Nalley's first pass on Bill's Turbo CB750 Purple Rain.There's 2 of them. Pleasa to download here. Then my dyno run is also there Bill's MinI Cobra 915cc 101.24 rwhp dyno run. Please post it in Calendar Girl thread and the dyno runs thread, thanks Bill  The dyno run is actually the 99.98 one.

[edwardmorris]

Trey's first pass is on YouTube. Under Trey Nalley's first pass on Bill's Turbo CB750 Purple Rain.There's 2 of them. Pleasa to download here. Then my dyno run is also there Bill's MinI Cobra 915cc 101.24 rwhp dyno run. Please post it in Calendar Girl thread and the dyno runs thread, thanks Bill  The dyno run is actually the 99.98 one.

Here you go Bill 

P1

P2

[Bill/BentON Racing]

Rafi,  thanks, Trey, next pass is in the 10's!!  Bill

[RP]

D, keep info coming. Carb size is fine, not adjustable as later Bendiix Zenith ones. Of course it ran out. Why we wanted to run 5-6 lbs with std or slightly retarded timing. You really think a young gun is going be watching the gauge? Not anyone's fault but mine, I knew what would happen....did!  . Exhaust not bigger, different design from Bill Hahn ,the creator. He probably knew what he was doing.  .  I'm going to keep it as simple as I can. Keep up with the input, I appreciate it!  Bill

I am not sure Bill Hahn always knew what he was doing.  His first turbo kits for Kawasaki Z1's did not have wastegates.

[Bill/BentON Racing]

Yeh, they blew up a few learning!  , Bill

[NitroHunter]

Bill sorry to see your sacrifice to the Aluminium Gods. Been there, done that. But once I replaced my bike's little pulse fuel pump with a Holley Red unit and adjustable regulator, the melted pistons stopped.  I ran 15 psi on ERC 110 gas but later shimmed up the barrels for lower compression. That's how the motor lived with 30+ psi boost on 118 fuel.

[Bill/BentON Racing]

Robbie, thanks, heading that way.  970cc turbo pistons, fuel pump and regulator, Dyna 4000 ignition. It will be a better package. Bill

[754]

Robbie our turbo hero who ran 10.0 on stock pistons.... He knows a bit about it.

[RP]

D, keep info coming. Carb size is fine, not adjustable as later Bendiix Zenith ones. Of course it ran out. Why we wanted to run 5-6 lbs with std or slightly retarded timing. You really think a young gun is going be watching the gauge? Not anyone's fault but mine, I knew what would happen....did!  . Exhaust not bigger, different design from Bill Hahn ,the creator. He probably knew what he was doing.  .  I'm going to keep it as simple as I can. Keep up with the input, I appreciate it!  Bill

Even at 6 psi you need to retard the timing a bunch.  If the young gun is not watching the gauge just install a check valve and release to hold the highest reading.