Cato
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That takes me back.
On mine, I had to elongate the the rear mount hole but there was nothing that could be done with the short header pipe.
I bet you could make a new section from the collector back, that looks like a Harris but far more refined and in stainless steel.
As you are mating the exhaust to the turbo, I’m guessing the the Harris headers will be redundant and the collector will be cut off?
Cato
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I won't be using an exhaust at all. It'll be a similar set up to the photo below but it'll be swept down rather than forward.
Wow! Yes that is awesome.
Would I be right in thinking that you have to manage the boost or power at lower RPM to stop the torque from stressing the internals?
I wondered if a bike would naturally restrict torque anyway, purely due to traction/wheelie issues.
Would I be right in thinking that you have to manage the boost or power at lower RPM to stop the torque from stressing the internals?
I wondered if a bike would naturally restrict torque anyway, purely due to traction/wheelie issues.
Cato
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A blow through turbo set up is a lot more user friendly for pottering about as the pressure is before the carb/injection. A draw through has to be ridden a lot more like two stroke as the pressure is after the carb and they will choke up if you potter about, sit at idle for too long etc.
Low rpm means low boost pressure as it's dependent on exhaust temp and velocity. So there's a natural moderation of boost, but with an older air cooled engine, especially one with a roller bearing crank you have to keep boost relatively low (single figures) anyway. With the engine I'm building up for this the limit will be around 200hp, so to give a bit of leeway I'll be aiming for around 180 hp at somewhere in the 6 - 8 psi of boost range.
Given that it's an old school set up the boost will be 'noticeable' when it kicks in.
I reckon that 180 hp on a 42 year old bike will be more than enough to keep things interesting. They're a bloody handful with the standard 100 hp.
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I had something similar on my GS850 at one point.
A blow through turbo set up is a lot more user friendly for pottering about as the pressure is before the carb/injection. A draw through has to be ridden a lot more like two stroke as the pressure is after the carb and they will choke up if you potter about, sit at idle for too long etc.
Low rpm means low boost pressure as it's dependent on exhaust temp and velocity. So there's a natural moderation of boost, but with an older air cooled engine, especially one with a roller bearing crank you have to keep boost relatively low (single figures) anyway. With the engine I'm building up for this the limit will be around 200hp, so to give a bit of leeway I'll be aiming for around 180 hp at somewhere in the 6 - 8 psi of boost range.
Given that it's an old school set up the boost will be 'noticeable' when it kicks in.
It was nice to have known you.
Cato
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A mini update on this one, I've spoken to the supplier of turbos and welder of exhausts and it's getting a nice roller bearing carbon seal turbo. A dear do, but it was never going to be a cheap build. 
I have a nice man milling a spacer plate up for the lock up clutch too. So although there's not much in the 'bolting it together' category things are moving along.
I've also picked up the wheels, I went for R6 wheels in the end as they look how I wanted without getting into Dymag levels of silly expense. They look pretty good in the JMC and Slabby front end I think. They'll need minimal work in the way of spacers and even the calliper position doesn't look as bad as I'd feared.
I have a nice man milling a spacer plate up for the lock up clutch too. So although there's not much in the 'bolting it together' category things are moving along.I've also picked up the wheels, I went for R6 wheels in the end as they look how I wanted without getting into Dymag levels of silly expense. They look pretty good in the JMC and Slabby front end I think. They'll need minimal work in the way of spacers and even the calliper position doesn't look as bad as I'd feared.
Morrisman
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I remember an article in Bike magazine, 30 or so years ago, Pip Highams z1000 with an American Turbo Pak draw through system on it. Nothing else was done, stock frame, brakes, wheels etc. Real old school.....
Cato
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They're a pressed up crank and the primary gear needs to be changed from helical to straight cut because of the power increase. If you don't the extra power from the primary gear loads up on the clutch gear and increases the thrust pressure on both the crank and the clutch. Welding the pin ends to the webs is also required to cope with the extra power as the crank can twist.
Jeepers! Serious engineering there - welding in itself can cause the crank to pull? Also, I'm guessing it needs welding with sufficient energy otherwise it's likely to crack at the welds?
The Yamaha crank in my xj650 has shell bearings and straight cut gears. Does that mean its good?
Cato
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It's not that straight cut gears are better for normal use, but if you consider that with the turbo it'll go from 100 hp to 220 ish you can see that it'll need to be uprated accordingly.
The welding isn't so much that it pulls them as it's two short welds and the pins/webs are pretty substantial. Looks like this when it's done, you can just see one weld each side of the pin end.
Pete.
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If you use a smallish modern roller bearing turbo on a blow-through it can be hard on the internals. They spool very quickly and produce massive torque at much lower revs than you might expect. Because of the low(ish) rpm your engine will be at peak cylinder pressure for longer (as the crank is turning slower) which can put massive strain on the crank and rods. On top of this the intake temps are higher for a given boost on a small turbo compared to a large one.
I made the mistake of fitting a GT28 turbo on my bike which was rated for my target power. This worked great but was a real handful getting off the line and just about unmanageable on wet roads. The guy who bought it was a motocross loving loon and he really enjoyed riding it though.
Pete.
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It would build boost sitting still if you held the brake and let the clutch out either a bit of throttle. In the wet even at small throttles it would spin the rear up, just pulling g away from lights you might have to shut off 2 or 3 times to stop the skin. No fun tip toeing everywhere.
Ahh, turbo too small then...
I'm toying with turboing my 650'seca lookalike 900F build. Just low boost, it's air cooled after all. The difficulty is that the charging system is struggling to run an efi pump allong with everything else, so maybe that will stop me..
I'm toying with turboing my 650'seca lookalike 900F build. Just low boost, it's air cooled after all. The difficulty is that the charging system is struggling to run an efi pump allong with everything else, so maybe that will stop me..
weldingnovice
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Wouldn't it be better to dowel the crank pins?
Cato
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It wouldn't be as strong as there's not enough meat in the cast webs to get a decent sized dowel. Two runs of weld about 25 mm long each side of the pin circumference is the accepted way to get enough extra agrip to stop any twist.
