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I need help with tuning a 90 pred Please
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Posted by: 03sp500

Hi all

I just finished the 90 pred and it seems good but need help with one thing, It has a Hetricks power up kit with the red springs and a 90 jet.

On take off there is no power the engine labors and slowly revs up,gaining speed gradually, once reved up it runs great all sorts of speed. if you keep the rpms up its a rocket, even if you come to a short stop. if you let it sit for 15 seconds or so the engine rpms come down and then the engine labors again to gain speed and rpm's

I also noticed that when driving around once up to speed, it seems to break up if you keep the rpms below a certin point, just a little more gas and it clears out and sounds smooth and sweet.

Any Ideas, is it jetting maybe ? or possibly stall speed? I am leaning away from stall speed (clutch stuff) because the engine seems labored on start up I think if it were clutch it would rev up just not take off.

Posted by: mcatvme

Whats the plug look like? Did you change the roller weights and lighten the clutch shoes? Need more info.

Posted by: 03sp500

Havent pulled the plug yet, but I spoke to Hetricks racing and they tell me its most likely a stall speed issue. I havent drilled the clutch but they said I should. It makes sense and after all they are Hetricks Racing. Has anyone else had to drill the clutch shoes? is it a common thing ?

Posted by: newnick

Since your using Hetricks parts you should follow their advice. They know how their parts work together and will help you get the performance you want, just explain what you want.

Posted by: 03sp500

I drilled some holes in the clutch shoes last night and it seemed to help. I will drill the rest tonight and I think that might do it.

They are very helpful at Hetricks thats why I went with them. I'm sure they will get all the wife's new floor money and some of the kid college money before we are done racing. LOL

Posted by: Livin4Real

what weight rollers are you running and have you changed the springs in the shoes?

Posted by: 03sp500

5.0g rollers and changed the shoe springs to red 2000 rpm springs