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Thread: cam and crank modifications

  1. #1
    drayday
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    I have an 87 gsxr with the 1255 piston kit, a Star Racing ported and polished head, no electronics,and a broken Cam Motion exhaust cam with a 365 lift. Drag bike only, running 6.20s (1/8 mile Texas tracks). It is suggested that I switch to a 355 lift cam, that I lighten the crank by taking the alternator off(still using stock starter), and that I get anMSD or Dyna 2000 ignition.Any thoughts on whether these mods will actually show improvements Edited by: drayday

  2. #2
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    the alternator being removed wont change your starter setup, you will just need to charge the batteryevery otherround. you dont lighten the crank by removing the alternator, just reduce drag being sucked by the alternator and to be honest i dont think it adds a ton of drag but removing it can only help. i dont see why going to a smaller cam would help perofrmance MSD and dyna are both good ingnitions, that being said unless your current system cant provide enough guts to fire your motor a loadyour probly not gonna see huge gains there, there wil be a gain but not huge ones.





    whats your bike/rider weight combo what broke the cam that cant be good.....





    i run .380 lift cams in my 1216 gsxr, no alternator and a dyna 2000 and run 5.70's @ 620lbs total
    1992 GSXR 1100 small tire dragbike 8.70\'s@155mph
    1998 RF900 Trac Dynamics Car tire chassis dragbike 8.20\'s@164 mph
    2001 Busa 9.64@142

  3. #3
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    Dang, i ran 6.50's on a stock motored 87 GSXR1100 with no bar, stock wheel base with only a V&H supersport pipe and 36mm flatslides, foot shifting. Something is not right with your bike if it only runs 6.20's.


    Like GSXR1216 said, something caused that cam to break. It should be thoroughly checked out before you install another cam.



  4. #4
    drayday
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    Thanks for the advice 1216. We broke the cam by re-installing it improperly(tightened bolts out of sequence). We have decided to go back with the same G4 cam although I'd rather go to a .370 lift(unsure if I have short valve guides but I doubt it). As for the alternator, I'll leave it be. As for the ignition, I'm still undecided. Dynatech said the dyna 4000 would not work well on this bike but the 2000 will. Got my eye on an affordable msd but still wandering ifit's really worth the money. Will I actually see increased performance I weigh 190lbs. Unsure about the bike but not lightened. I'm impressed with your times 1216. Dragracer,youhurt my feelings[img]smileys/smiley19.gif[/img]. I thought I was running hard.


    Edited by: drayday

  5. #5
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    drayday,





    .380 should fit on stock guides. MSD isnt a bad ignition either if the price is right.





    man if your only 190lb something else must be way off in your combo, my stock ( stock tires, gearing, wheelbase) hayabusa runs 6.40'sin the 1/8th with my 225lb suited body on it, a well set up 1255 should run much better!





    good luck!


    1992 GSXR 1100 small tire dragbike 8.70\'s@155mph
    1998 RF900 Trac Dynamics Car tire chassis dragbike 8.20\'s@164 mph
    2001 Busa 9.64@142

  6. #6
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    Sorry bud, wan't trying to hurt your feelings just giving you a baseline. GSXR1216 is correct. Something is not quite right with your combination. There aren't to many ways to assemble a bottom end but there are lots of variables in the top end. After you get it assembled again and make a few passes, please do a leak down. My guess is you've got a problem with the head. A buddy of mine with a ported oil cooled head with stock cams, 1216, weighing 240 lbs ran5.80's with his bike. I feel your problem could be in the head. By the way, you didn't tell us if this was a no bar bike or slick and bars. That makes a difference.

  7. #7
    drayday
    Guest
    Thanks guys. This motor was put together by a guy in Baton Rouge around '98 or '99. I bought the bike in 2000. Have raced it everysince without any tuneups or going in the motor. The previous owner recently admitted the bike did not do what that mechanic promised it would. Felt they overpayed(around $4000 on the motor alone). Current mechanic said motor looks good,runs strong,has Some good parts(Star head,good pistons,valves,etc)but should do better. Will take your advice Dragracer and do a leak down(never done before). Sprockets are 13/45,cams are 365lift exaust/400lift intake,Vance and Hines sidewinder,badly tuned 38 mikuni flatsides.I am running slick and bars. 1.39/1.45 60 foot. Stock ignition with no electronics(no tach or 2 step for consistent launchs,stock rev limit). Really want to add 40mm lectrons and nitrous and bedone but finances holding me back.I accept constructive criticism and advice very well. Thanks for the help thus far. Edited by: drayday

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    what size rear tire


    IMO your gears are WAY off for a slick and bar setup, i run 14-54, seeing as yours is slower you should be geared even lower than that and your actually geared higher than mine. personally i wouldnt run a 13 tooth, wraps the chain real tight, beats up chains.....


    toss the 38's on ebay and at least get 40 mikuni if not lectrons. personally i dont think ignition is holding you back compared to other things.


    i find it funny someone payed $4000 just for a motor and i cant get $7700 for my complete bike turnkey.........
    1992 GSXR 1100 small tire dragbike 8.70\'s@155mph
    1998 RF900 Trac Dynamics Car tire chassis dragbike 8.20\'s@164 mph
    2001 Busa 9.64@142

  9. #9
    drayday
    Guest


    Hey 1216, I'm running an 8in Mickey Thompson. I've heard that about the 13 front sprocket. What do you suggest on the front and rear and how can I really tell if the chain needs replacing It looks ok to me. WillI have to add links with thesprocket changes Funny thing too,when I put the motor back on the frame after the tranny install the chain became very tight. Did replace the front sprocket but with another 13. No other changes there andall mounting brackets lined up. Can't get anymore slack out of it and it is almost(some say) too tight. I hear so much about the Lectrons. Would you say that 40 Mikunis are just as good What are your thoughts on my cam sizes(365lift ex/400lift in). Also the book says you have to have short valve guides for over 370 lift. Mechanic says I have short guides or submerged guides.


    Edited by: drayday

  10. #10
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    they dont make a 8" mickey to my knowledge sure its not a 25x7" thats what i run





    cant really tell you what gears you need, all that is based on what you can get for in trap speed. all i can tell you is your bike is slower than mine so it should be geared lower than mine to help make up for the lesser amount of HP. chances are you will need a new chain since your wouldbe too short going to bigger rear sprocket. i would suggest watching ebay for some used sprockets since you dont know exactly where you need to be for gears, or download one of those gear programs input all your gear ratios ETC and what you think the bike can trap at and see what it says for gears to run.





    stock guides can take .380 lift, just double check the clearance to make sure that the clearance is indeed there, if someone repalced them who knows where they are for height better safe than sorry and check it out first!





    40mm are NOT as good as lectrons plain and simple.... but 40's would work better than the 38's you have, hell the '88-89 750 came stock with 38mm carbs. you need bigger carbs. even a set of 38 trons would be a upgrade, sometimes they go cheap on ebay since not many people run 38's.
    1992 GSXR 1100 small tire dragbike 8.70\'s@155mph
    1998 RF900 Trac Dynamics Car tire chassis dragbike 8.20\'s@164 mph
    2001 Busa 9.64@142

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