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Discussion Starter · #1 ·
Hi,
I've got a problem that I hope someone can help me with. The problem is that the raptor seems to top out at 55-56 MPH, which seems a bit low?. It previously ran a 40T rear sprocket, until recently when I changed it for a 38T, but this has still not made much difference. The front sprocket I would believe is a 15T or 13T, I will need to confirm this. It sits at roughly 9000RPM in 5th at the top speed. What top speed should 13/38 gearing result in?. The quadbike is stock.

Any advice would be appreciated.

Thanks.
 

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If the engine is stock and you are gearing it up then the motor dont have enough power to wind out. When you say it goes up to 9000 rpm you mean when you just rev it in neutral right? It would go faster if you geared it down. Maybe put the 40 tooth back on the rear and put a 12 on the front. Stock is 13 front and 40 rear and mine would go 73 when it was stock.
 

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Discussion Starter · #3 ·
If the engine is stock and you are gearing it up then the motor dont have enough power to wind out. When you say it goes up to 9000 rpm you mean when you just rev it in neutral right? It would go faster if you geared it down. Maybe put the 40 tooth back on the rear and put a 12 on the front. Stock is 13 front and 40 rear and mine would go 73 when it was stock.
Well no, not in neutral. I've set the shift light on the speedo at 9000RPM as this is when I shift and what the speedo displays at the point. It also seems to rev way past 9000rpm, as I've caught it at 10500RPM when ive shifted a bit late. Could it be possible the speedo is out, or could this possibly be the result of a bigger problem?. As far as I'm aware the quad is stock.
 

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Ya that dont sound right to me dude. What are you using to measure rpm and speed? I used a gps to measure my speed when i did it. I have no idea how high mine will rev but 1050 seems pretty hi to me. Hopefully someone else will chime in and shed some light.
 

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Master of the Electron
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What rear tire size? What air pressure?

13/40 is stock gearing. With stock gearing and stock tires, top speed should be high 60's to mid 70's depending upon what mods the engine has (if any). 75 is the absolute limit stock, due to the built in speed limiter in the CDI.

Unless your CDI is not stock, the engine won't rev to 9000. It is limited at 8500, if I recall.
 

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Hi,
I've got a problem that I hope someone can help me with. The problem is that the raptor seems to top out at 55-56 MPH, which seems a bit low?. It previously ran a 40T rear sprocket, until recently when I changed it for a 38T, but this has still not made much difference. The front sprocket I would believe is a 15T or 13T, I will need to confirm this. It sits at roughly 9000RPM in 5th at the top speed. What top speed should 13/38 gearing result in?. The quadbike is stock.

Any advice would be appreciated.

Thanks.
Well no, not in neutral. I've set the shift light on the speedo at 9000RPM as this is when I shift and what the speedo displays at the point. It also seems to rev way past 9000rpm, as I've caught it at 10500RPM when ive shifted a bit late. Could it be possible the speedo is out, or could this possibly be the result of a bigger problem?. As far as I'm aware the quad is stock.
Sorry to tell you this, but a stock 660 Raptor engine will never rev past 7800 rpm, not even much higher with it in neutral.............
The stock rev limiter will stop it at slightly over 8000 rpm, and secondly, the way the engine is designed, it just cant pull much higher then 7500 rpm in 4th or 5th gear. With the 13 - 40 gears which is stock, the atv is limited to about 73 mph, the trans output shaft has a sensor that will back the timing off when you hit this speed, trying to override this sensor electrically is a bit of a chore, I accomplished this by removing most of the teeth from the reluctor wheel.
My oval tracker used 12 - 48 gears and would pull 80 mph in fifth at 9300 rpm with 19.5 inch tires..............but it sure wasnt stock........:D:D
 

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Check your clutch. If you are actually running high rpm and still going slow your clutch may be slipping. Mine slipped and it would not go as fast. One simple check is to put it in a higher gear and go WOT. If it revs up, and then settles down as it picks up speed your clutch is burnt and the problem is found.

If you know your clutch is fine then it is likely gearing, tires, excessive weight etc.

If your tach is wrong it could be improper jetting holding down rpm, but if it was a carb issue you would notice odd sputters pops etc.

Just my 2 cents
 

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Well no, not in neutral. I've set the shift light on the speedo at 9000RPM as this is when I shift and what the speedo displays at the point. It also seems to rev way past 9000rpm, as I've caught it at 10500RPM when ive shifted a bit late. Could it be possible the speedo is out, or could this possibly be the result of a bigger problem?. As far as I'm aware the quad is stock.
Shift light, speedo..... and u said 660 right?
 

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Discussion Starter · #9 ·
Yes, the quad certainly is a raptor 660. The speedo is aftermarket which also has a shift light which can be set to desired RPM. Tires size is 18inch, although I'm not sure about air pressure. The clutch is also fine as I've tested this on a steep hill and there seems to be no slippage from the clutch. I can only guess then that the speedo might be at fault, giving an incorrect reading of RPMs?. Thanks for the input.
 

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I have 14-40 Gearing with 21" rear tires. It also has the Big Gun OverRev CDI and I topped mine out right after getting the new sprockets and I was clocked at 81 mph
 

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Well if your running 18 inch tires that will give you a lower top speed. Stock is 20 in the rear and 21 in the front. Im betting your speedo is off and giving you a false reading on rpm and probably speed. Try checking your top speed with a gps and see how close it is.
 

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Master of the Electron
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THe shift light runs from a tachometer that expects one spark pulse per every two engine rotations (4 stroke) - the Rappy genereates a spark EVERY rotation (one is wasted) - you could well be displaying twice the RPM that the engine is really turning.
 

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Discussion Starter · #13 ·
THe shift light runs from a tachometer that expects one spark pulse per every two engine rotations (4 stroke) - the Rappy genereates a spark EVERY rotation (one is wasted) - you could well be displaying twice the RPM that the engine is really turning.
I would say that sounds like a realistic problem, as the engine is willing to rev past 9000RPM, whilst 5th is engaged. What steps can I take in order to check if the problem is what you have stated, and rectify it?
 

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Master of the Electron
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I would say that sounds like a realistic problem, as the engine is willing to rev past 9000RPM, whilst 5th is engaged. What steps can I take in order to check if the problem is what you have stated, and rectify it?
It's simply a function of the tach/shift light you're using... since they are aftermarket, you're going to have to investigate how they're programmed for operation on different vehicles/engine types.
 

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I would say that sounds like a realistic problem, as the engine is willing to rev past 9000RPM, whilst 5th is engaged. What steps can I take in order to check if the problem is what you have stated, and rectify it?
Check to see if your tach can be programmed. It may have switches for this on the backside of the tach........
 
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