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Author Topic: Slow off the line  (Read 2134 times)

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Offline Gavinator

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Slow off the line
« on: August 27, 2014, 02:51:27 PM »
Hi all,
 The 750A is new to me. My son has a modified Jr Dragster that has the 750A on it.  It is very slow off the line! It will get up to speed but takes forever and only hits about 52 mph in 1/4 mile.
 A friend said it seems like problem may be in torque converter or trans..
 Any suggestions where I should start?
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Offline dave the welder

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Re: Slow off the line
« Reply #1 on: August 27, 2014, 03:29:39 PM »
what is the final gear ratio you are using????you might check into a bigger rear sprocket or a smaller front.
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Offline Gavinator

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Re: Slow off the line
« Reply #2 on: August 27, 2014, 06:56:01 PM »
I'm not sure. But thanks for the suggestion.
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Offline dave the welder

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Re: Slow off the line
« Reply #3 on: August 28, 2014, 02:25:17 PM »
this my be a dumb question but is your son starting in low and once the motor is reved up pretty good is he then shifting into high gear?if he is just using high gear it's no wonder its slow
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Offline Gavinator

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Re: Slow off the line
« Reply #4 on: August 28, 2014, 02:47:45 PM »
No such thing as dumb. Believe me, I feel dumb.  This is all new to me.  He is starting in 1st and really could go the whole 1/4 without needing to shift to 2nd the way it is acting right now.
 Also, I forgot to mention that it wants to die when you first put it into gear which is why my buddy was thing it may be a problem trans/converter.
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Offline raymond10078

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Re: Slow off the line
« Reply #5 on: August 29, 2014, 06:01:35 PM »
A stock CB750a would do much better than that in the 1/4 mile . . . but I doubt you have a converter problem.

What have you done to tune the engine and make sure it runs properly?
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1978 CB750A (upgrading very, very slowly)

Past bikes - Honda: SL350, CX650C, CB900C, CB1000C, CM450A; Kawasaki: several 1972 750 H2's; Suzuki: TC90J.

Bikes I want: CX650ED, a mid-sized japanese V-twin with ABS.

Offline Gavinator

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Re: Slow off the line
« Reply #6 on: August 30, 2014, 02:34:24 AM »
Not a whole lot yet.  Just got it running. It is very much a homemade mess if you know what I mean. Had to clean up all the wiring on it and some welding. It does need tuning which I am trying to get to.  Hope to spend some time on it this weekend. Thanks
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Offline Gavinator

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Re: Slow off the line
« Reply #7 on: September 01, 2014, 03:36:58 PM »
Just an update guys.  Found timing and points off and a bad coil.  Getting new coil. Hope that takes care of it. Thanks, Bill
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Offline Gavinator

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Re: Slow off the line
« Reply #8 on: September 14, 2014, 03:26:23 AM »
Hey Kandrtech , Just wanted to give an update.  After replacing bad coil, adjusting the timing and points we have now reached 78 mph in the quarter. Seams to be running lean. Thinking about rejetting carbs.. Also running open header. Someone suggested that I should have a muffler on it because back pressure will help. 
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Offline dave the welder

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Re: Slow off the line
« Reply #9 on: September 14, 2014, 07:56:48 AM »
if you are running the stock carbs you  definitely need to richen up the carbs especially with open exhaust.
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Offline Gavinator

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Re: Slow off the line
« Reply #10 on: September 21, 2014, 06:36:52 PM »
Thanks Dave.  Still tweakin it.  Will definately do that.  Will try to post some pics next.
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Offline Gavinator

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Re: Slow off the line
« Reply #11 on: September 21, 2014, 07:08:01 PM »
Hope this pic shows up.  Best I have right now.
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