CRF450 popping

I installed the no toil super flow kit and have started running 110 octane. The bike pops alot when you let off the throttle. I know it needs re-jetting, just was wondering exactly what i needed to do?

Did you get a high compression piston? Otherwise the high octane gas isn't really necessary.

Anyways, the pilot jet in the carb needs to be cleaned out or you need to adjust the fuel screw at the bottom of the carb. If you adjust it and it's more than 3 turns out, get a bigger pilot jet and re-adjust the fuel screw.

I decided to run the high octane fuel to get rid of the ethanol in regular gas. Is the ethanol not really a big deal in these bikes?

First, run the fuel grade designated for your bike. Doubtful the 110 is causing or contributing to the popping but it is not good for your bike. I assume the 110 is AVgas, right (even worse)?

Popping is a lean condition when the throttle is closed. On trail bikes with mufflers, they pop but the muffler quenches it so you cannot hear it. Trail bikes also have a carb decel circuit called an ACV (Automatic Coast Valve) that adds fuel to compensate for the lean condition during decel. Race bikes have open pipes and many owners put on pipes that are even more open. Additionally, they do not have an ACV.

Race bikes are meant to be raced. WOT then 100% on the brakes. You do not coast when racing.

So... popping is a fact of life for trail riding a race bike. Now, there re things that can contribute to decel popping.

  • Check the exhaust for air leaks. Hold a towel over the end of the muffler and listen for hissing, signifying a leak. Leaks can happen due to a fall or worn out gaskets.
  • Confirm your hot start works properly and is fully seated and does not move as the bars are turned.
  • Check for a vacuum leak by using a mild non-flammable spray solvent
  • Confirm your fuel screw is properly set for a perfect idle with a hot engine.

^^^If the OP is running oxygen rich race fuel (??110??) then it will need to be re-jetted thru' out.

I doubt it is VP or the like, I am sure it AvGas. 110 Race fuel is horribly expensive. Also, I am sure this guy does not need that tiny added boost race fuel can give because 'his bike is too slow'.

I think it is a misguided attempt at simply getting fuel without ethanol. I certainly do not blame him. In VA, the only place you can get clean fuel is at the boat docks, on a boat fuel can.

I thought as much.....

On the crfs, the only time that you would need race gas is if you put a high compression piston that is past 13.5:1. I run premium pump with 10% ethanol and the bike runs just fine. So, if you are running a h/c piston with a compression ratio 13.5:1 or below, you are throwing money away with 110.... Check out the crf 450r forum and there are a lot of answers awaiting.... I would start by checking out your jetting and making sure that your exhaust gaskets are in good shape, that is one problem that can cause your symptom.

the exhaust is leaking where the end of the pipe is bolted onto the main body of the pipe. new packing? and the fuel is sunoco race fuel. is it not wise to run it?

Repair the leak. Packing is the stuffing inside the muffler. As you run the bike, it gets worn out. It lasts between five and fiteen hours on an aftermarket pipe, maybe 50 hours on an OEM pipe.

Do not run race fuel. Higher octane than the bike was designed to run on actually makes less power as well as wasting money. The rule of thumb is to run the lowest octane you can and not get pinging/detonation.

thanks guys:thumbsup:

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