Why is my friends bike faster than mine??

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alexjordan22

New Member
#1
#1
Here's the deal. We both have Baja Warrior bikes. His bike is bone stock with the baja engine on it (196cc??) And a GTC torque converter. Stock 50 tooth rear sprocket, stock rear tire. He weighs about 60 lbs more than me.

Now my bike has a taller rear tire diameter, stock 50 tooth sprocket, it has a HF 6.5 with the NR racing stage 1 hop up kit which includes:

4 degree advance key
Hi flow air filter
Bigger jet for stock carb
18lb springs

I also made a header and installed the Autolite racing plug. This engine with the same torque converter has similar off the line performance, but he pulls away from me in top speed easily. And I'm lighter!! Something is wrong somewhere but I just don't know what yet.

We compression checked our motors, his was just under 60 psi and mine was right about 45 psi (no idea what's normal)

Anyone have any ideas?? My logic tells me I should be spanking him without question.
 
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alexjordan22

New Member
#5
#5
I suspect valve lash as well, and I plan to check that next weekend when I get back down to where the bike is. However our gearing is the same. Same TC with green spring hooked in the center hole of the driver, 50T rear sprocket.

The governor being hooked up differently can matter? Both of our throttles open fully so I would figure wed have the same amount of air coming in no matter how the cable is hooked up, just as long as it opens all the way right?
 
C

Camjamsdad

Active Member
#6
#6
I have 2 predators. The old one is listed as 3600 rpm, the new one is listed at 3800 rpm. So there are differences. I've also seen pistons flush in the hole and a couple noticeably down in the hole. So compression ratios can be a factor.

I doubt your gearing is identical. You may share the same tooth count but you'd have to measure both tire diameters to be able to say 100% the same ratios.

Tire pressures, bearings adjusted the same, binding bearings, same air filters, dirty air filter, clutches slip, brakes drag, unlubed chains, loose chains, tight chains, new engine, broke in engine.

Many reasons.
 
hornet1

hornet1

New Member
#7
#7
Reaction time is every thing / plus your both different on tire size weight and looks like everything else . Get a hole shot and never let off.
 
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alexjordan22

New Member
#8
#8
Yes I've got him off the line, but at full throttle he will slowly walk on me pulling away. He'd be in back and it'd be about even, then he'd slowly start to pull on me and continue. It sort of sounds like my engine at WOT is at a lower rpm than his is. I have a 26mm Mikuni lying around that I'm considering putting on and tuning, but I really think I need one of them fancy Guardrail Dave rear sprockets to help me with my top speed.

The converter gives me more than enough low end power, but I just need a bit more top speed you know?
 
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JKautoFab

Active Member
#9
#9
sometimes throwing parts at an engine does not always make it faster. My guy has a dyno to track what gains and possible losses mods can have. just because you got a different jet doesnt mean you got the right one for your motor. as camjam said, motor can be different even ones you would think are the same, china changes stuff all the time! you should see what they do when they run out of the right size bolt...
 
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alexjordan22

New Member
#10
#10
Yeah I understand that. Im not new to these engines just to this forum. Originally I was curious if anyone had any input on what I should be looking for as far as problems with the engine go. Ive never had a modded engine be slower than an unmodded one. Simple as that. Yes, tire pressure and bearings and other things have a factor in it, but something isn't right. The engine doesn't feel as powerful as it used to and I was curious if anyone else may know why.

Again, hes got a good 60 lbs on me, a 196cc 6.5 with just a header, same TCs and rear sprocket as me.

I have a TALLER rear tire which should equate to a higher top speed, and quite a few more engine mods than his engine. But my compression was much lower at 45 psi to his 60.

Ill track down a rear sprocket to help with the top end...but something just isn't right with this engine at the moment. I know you know what I mean...when you ride it and you're like....:shrug:

So Ill dig deeper into it this weekend. Maybe do a few plug chops and see how my jet stacks up. Anything you think of that I havent mentioned yet will help. Thanks everyone.
 
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alexjordan22

New Member
#12
#12
Right? The weight difference alone should make me faster, but even with the weight difference AND my mods im still slower. Jetting might be the issue I think too. That and I haven't checked the valve lash after installing the 18 lb springs over a year ago, so I may be losing some power there if it's not set right. Ill order up some jets and play with it a little. see if it's lean or rich. Thanks.
 
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alexjordan22

New Member
#17
#17
Washington State. I live in Issaquah and the bike is in Puyallup. The place where my bike is at isn't owned by the friend I keep losing to, it's owned by another friend and he just has the Garage space for us to keep our bikes there.
 
ole4

ole4

#18
#18
How much taller is your rear tire? With that tire you are not really geared the same as tire diameter factors into this. You may be overgeared when the TC goes into overdrive and the motor cant pull it.
 
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alexjordan22

New Member
#19
#19
That's actually a good point....I didn't think of it that way. I could swap him rear tires and see what happens...that might be the issue. Unless I could get the torque converter to shift into overdrive a little later which would.give my motor a bit more time at higher rpms to gain some speed. It is quite a bit taller, I didn't think to measure it but it's pretty close to the rear fender. That's interesting.
 
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