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Discussion Starter · #1 ·
I've ported my 98 750 and found out that instead of gaining power mine loose...

The rpm increases faster than before but I'm not sure about the torque...
Anyone has an idea how to fix this problem.
While surfing the net I've found a guy called "Motoman" who suggests to reduce the intake prots by 30% instead of widening them...
For those who might be interested in this issue check this web page
"www.mototuneusa.com"


[ 11-15-2002, 01:56 AM: Message edited by: cenkesener ]
 

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the best way but not the cheapest get your old head bench flowed reported if you did it then get another one do as the web-site says see which one is better. then you know vs what some way say gsxrfreak has a 600 head on his 750
 

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Well it is on my friends bike.. not mine...

As for power output.. We are not to sure.. HIs rings are really old and he didnt want to spend the money for new rings...

We have had it on a mustang Dyno. It pumped out like 117hp and it was one of the smoothest power curves I have ever seen for not being custom mapped.. We did have a yosh black box put on it, and the bike has like a .5hp dip at about 6K RPM... The power comes on at like 6500K and pulls up to about 13,500K before the power starts to drop off..


Anyhow.. I agree that smaller ports are better, but not always more power...

John
 

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Yeah,that motoman has some good ideas out there. It does make sense to make the intake ports smaller as they would increase the velocity.Sportster's have already proven this with an 883 head on the 1200 jugs.The 883 heads made more power than stock 1200 heads.And this idea came from Hardley's.I think maybe a big bore could get you back some power.A really big bore
 

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Discussion Starter · #5 ·
I'm not sure whether smaller ports would necessarily mena higher torque as I need this to be done for drag racing...
Anyway , I'm also not sure using epoxy to make the intakes smaller as the elasticity of epoxy is much more different than the material used to built the head. Expoxy being less resistant to heat , might easily break into small pieces...

Anyway thanks a lot for your replies...
 

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if you are looking to make power for drag racing that mototune stuff doesn't apply...when porting a head for drag racing and road racing you have to use two different approaches since you want the bike to make power in two different ways...mototune is dead on when it comes to making a smooth power curve for smooth power delivery...in drag racing you are looking for more peak power than smooth power delivery sorta speak...as for your head, it can be fixed but to be honest i would have to see it...and as for the epoxy, there is some on the market that will withstand over 350 degrees of heat and will not move...we use it in all the heads that we do for serious drag racers that require epoxy in the ports...if you like i can get you some of that epoxy but i must warn you up front that it is expensive!!!!it is used by all the prostock engine builders and is a highly guarded secret...

dwayne
 

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Discussion Starter · #7 ·
Dwayne thanks a lot for the info , but having visited once more Motoman's web site I see that motoman is getting 108hp as a result of a downward slope which wouldn't be usefull at drag racing as you've mentioned.
I better use my bike as it is as I can not afford anything else for the moment...
 
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