I'm noticing now that my 650i is not as stought out of the hole as when it was new. When i first got it, it would loft the front end up if you punched the throttle on pavement, it wrapped up rpm's quick. Now at 1480 miles or so, had new belt put on at 928,(didnt need it but mechanic put on anyway) I can punch it now, and its like a small hesitation, and it doesnt rev up nothing like it did new, after your already rolling though the power feels the same. It'll scat ***. Things i have considered are that i have not had it in to get the valves adjusted, or the carbs readjusted. I thought belt deflection may be a possibility, but it still achieves the same topspeed so i dont know. I hope someone may have some ideas because one thing is for sure, it definitely is not as strong from a dead start as it was, doesnt even want to loft the front end at all.

 

You haven't done any valve adj and have 1480 miles? That's way over due. The valves will dig into the head valve seat area requiring 3 angle head job or even a replacement. I would check/adjust valve every 500 mile interval at the most.
1. Check/adjust valve.
2. Check/adjust cam timing.
3. Check cam shaft lobe wear.
4. Do leak-down test to see if your mill is holding pressure OK or not.
5. Read plugs to check carburetion.

 

I want to say its your belt. Its very easy to check and maintain your belt. Go to www.nyrocatv.com and go to the tech tips section. All the belt stuff you need to know about is under the prairie section (same belt set up) read trough it and youll be your own machanic. A loose belt will cause loss of performance.

 

Original poster stated the engine does not rev up as it used to. Loose belt does not cause such engine revving up problem. Engine performance itself has nothing to do with the belt. Vehicle performance would be affected by the condition of the belt. Also, he said the top speed remains the same as before. The loose belt means larger effective diameter of the belt. Since the loose belt would be riding on the outer side of the driven converter sheave (like bike having a larger rear sprocket), the top speed would be less than before. Based on what the original poster has given and assuming his observation was correct, the problem points to the engine not the belt.

 

Doesnt hurt to check the belt along with the valves being adjusted i would say.

 

I assure you my observations are correct. I didnt think it was the belt either that is why i said the top speed was still the same. I figured that meant the belt was seated properly in the pulleys. I know that the valve adjustment is overdue but i did not get a free service from my dealer and i have not been able to afford to have it done. Heck my buddies 07 750 Brute is nearing 3000 miles and it is a week newer than mine and he hasnt had jack crap servicing done. I am selling an old custom truck of mine very soon and will have the valve adjustment done and was thinking of having a Dayco belt put on, or what is the best one you recommend Hayashi? Oh and the best way i can describe the situation is like its not getting the gas as fast as i hit the throttle, its simply not wrapping rpms as fast off the line as it did when it was new. Thanks in advance -Joe

 

Dont get a dayco belt. Stock is the best belt

 

Try to learn how to adjuve valves by yourself. If you have a service manual, it's a piece of cake. As for the tools, all you need are; a feeler gauge, flat tip screwdriver and a 10 mm box wrench. Set the piston to TDC and check/adjust. The hardest part is removing the fenders and gizzillion screws holding them on the 750 - it is the most time consuming quad I've ever worked on as far as removing the bodywork goes. Anyeay, doing the work by yourself not only saves $$ and time, it would give you the pride and confidence and you would learn more about your toy.
There are cheaper belts out there and Dayco is one of them. I still like the Kawi's OEM double cogged belt the best for their durability. Their price has come down quite a bit a couple of years ago and it seems to last longer these days.
Your bogging problem could be as simple as the sticking choke. Actually, there is no choke butterfly valve as you would see on 2-stroke motors and on some 4-strokes. The choke on the 750 is actually a fuel enrichener. So, choke is a misleading term. When push the choke to ON position, you are opening 2 plungers, one on each carb, letting in more fuel in the pilot circuit of the carbs. If the plunger (small cylindrical shape metal in the bore) is sticking in the bore due to corrosion or debris, it would be leaking in fuel EVEN if the choke lever on the handlebar is at off position. You will be running too rich all the time and the engine would be bogging especially when trying to accelerate. Follow the choke cable toward the carbs. It would become 2 separate cables at the end, leading to each carb. Just follow each end where the plunger is attached to.