Topic: Turbo guys I need some tuning advice

[76kcafe]

I have a 74 cb750 that is now a 836 wih an ATP turbo kit running 8psi. I am using a hsr42 carb. I took it to get dyno tuned and they said the carb is too big. So they made a restrictor plate to lessen the air flow. I got the bike back and it cuts out at 4,000rpm and won't go higher. I took the bike back to e place today and in the dyno it goes off the chart lean and then riches up to normal at about 6,000 all the way to 10,000. So now I am tuning it myself. Do any of you guys run an hsr42? If anyone has had this similar issue please let me know the cause. Thanks in advance.

[TurboD]

I agree it is on the big side. Is the pump working ok? Where and how big is the restrictor?

[76kcafe]

Pump is working fine. It covers almost half of the air inlet

[TurboD]

Interesting, I could see that giving the air bleeds all kinds of havoc. I would rather see you source out a Bendix (38mm) or possibly a smaller flat slide. BTW did you get a good pull,  what kind of power did it make?

[76kcafe]

Only 85hp at the wheel. So I am thinking it is just very lean. I would think it would make more power. I would really like to make this carb work if possible.

[scottly]

Did you get a copy of the dyno graphs both before and after the restriction was added? I'd like to see a picture of that tuning "solution".

[Bill/BentON Racing]

Yeh, that would help. Terry Kizer still out there doing turbo's etc. Contact him. Jim F has number,he may chime in or PM him. My first thoughts were how glad I was to have Brian Livengood and his great dyno work helping me! The man is awesome! Quite the talent and helluva nice guy, wife too, she not only looks better, she's even nicer!  Brian's R6 engines break 150 rwhp! When I met him he was at 143! Won 3 600cc races in a row with Dane Westby this year! Beating the factory bikes! 
Good luck, Bill

[76kcafe]

I don't have the graphs but I saw them on his computer and it did look as though it fixed the concern. The graph looked nice and smooth. The day he finished the bike I took it home and it won't go past 4,000rpm. So I am not sure what changed.

[Jim F]

What was your air/fuel reading?
I have a 42 on mine that was set up by terry
Kizer at mr.turbo
Call terry and he will spend as much
Time as possible to get you on track
Keep us posted
Jim