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alfa

should I use race gas on an 05 yz 450

17 posts in this topic

I have a major bog problem with the bike? It has zero power. The guy I bought it from used race gas and I put in 91 pump gas. It now runs horrible. Could the gas be the problem or could it be something extremly different.

I have to really be on the clutch so it will not stall and even then it is ready to die. When I got it I changed the oil, air filter, and sparkplug. The only difference it the gas.

The jetting is almost stock, according to the manual, and it has an FMF powerbomb header and T-4 exhaust.

I still need to check the valves, but the power loss is so extreme and I have never ridden a bike that is so bad, but could the gas be the problem?

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I would check the carb - it sounds like it may be gummed up inside and time for a complete cleaning, jets inlets etc.... Also check the diaphram. Race gas will not majically make it run better if these are your symptoms today with pump gas. Make sure the pump gas is not fouled:thumbsup:

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I pulled the carb apart and cleaned everything out, except the accelerator pump. But with it off, I turned the throttle, gas shot out, so I didn't remove it. It has an aftermarket pump cover, it is not a Boyesson, the cover is red, but I do not know what kind it is. I forgot to clean the tank, and put a gas filter on the line, but but when there is no load on the motor, (on the bike stand), it seems fine except for some small backfire on deceleration.

When riding in the pit area, in 1st gear I have to use clutch to keep the motor from dying. It just seems to be more than just the jetting. Could such a loss of power be from just jetting?

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I pulled the carb apart and cleaned everything out, except the accelerator pump. But with it off, I turned the throttle, gas shot out, so I didn't remove it. It has an aftermarket pump cover, it is not a Boyesson, the cover is red, but I do not know what kind it is. I forgot to clean the tank, and put a gas filter on the line, but but when there is no load on the motor, (on the bike stand), it seems fine except for some small backfire on deceleration.

When riding in the pit area, in 1st gear I have to use clutch to keep the motor from dying. It just seems to be more than just the jetting. Could such a loss of power be from just jetting?

does it idle and idle correctly? The popping is normal for a cold bike - you can adjust fuel screw when it is warm to adjust this popping condition from being lean/rich out. Red cover? P38 or ScaryFast cover I assume

Is the TPS unplugged or plugged in at top of carb? May be CDI related...

Anyone else have any opinion?

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One thing I did notice is that I had to turn the idle adjustment screw almost all the way in to to get it to idle correctly. The fuel screw is turned about 3/4 turns out. I have newer messed with the TPS wires but the marks on the top of it and the carb seems to be in the stock location.

When you say CDI do you mean the coil or the ignition box by the triple clamps.

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One thing I did notice is that I had to turn the idle adjustment screw almost all the way in to to get it to idle correctly. The fuel screw is turned about 3/4 turns out. I have newer messed with the TPS wires but the marks on the top of it and the carb seems to be in the stock location.

When you say CDI do you mean the coil or the ignition box by the triple clamps.

3/4 turns out? It should be closer to 1.5 - 2.5 turns out...sounds like jetting may be part of the issue

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I don't know of any engine mods, but if it did, would not running race gas be a problem.

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If he put a high compression piston in , THAN you will need 100 octane or so. If it has the stock piston, than you ONLY need 91 octane pump gas.

First make sure you're Hot start isn't sticking. The hot start plunger is notorious for hanging up (due to galvanic action) GENTLY unscrew the Hot start where it screws into the carb (it's Plastic and easy to strip) Make sure the plunger is able to slide up and down. If it's sticking, it will cause a lean condition. Lube the plunger with a film of waterproof grease, to prevent future seizing.

From what you wrote, it sounds like a lean condition to me. First I would do is get the fuel screw adjusted correctly. This makes a Major difference from idle to 1/4 throttle or so. Also, I'm assuming your weather has gotten colder, so this only worsens the lean condition.

To set the Fuel screw:

1) Make sure bike's fully warmed up

2) Place bike in neutral, place on stand (or side stand), start it up.

3) Turn the idle screw in to acheive a faster than normal idle

4) Slowly turn in the FUEL screw, (turning it in is leaning it out) you will start to hear the RPM drop, and it will almost get close to stalling.

5) Start turning the FUEL screw out, slowly until you acheive maximum RPM.

6) At this point, you will be pretty darn close to the Optimal setting. Really fine tune it, by cracking the throttle, and listening. You want to hear a nice crisp tone, instead of a burbly sound like the exhaust is under water. Like I stated before, the optimum setting will be near the maximum RPM point, or within a 1/4 turn in or out.

7) Once you think you have the optimum setting, shut the bike off, and mark how far out the fuel screw is from being fully turned in (count how many turns it takes to get it fully in, from where you were)

8) Turn the fuel screw back out the number of turns you counted from being fully in. THis is your baseline for the day.

hope this helps.

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The race gas did not work. Could the problem be with the electrical. I will try to disconnect the TPS to see if there is a change in performance. I will also try to clean the carb fully. Anyone have any ideas with the accelerator pump. I have a scaryfast. Could it not be installed properly?

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Well, I tried race gas, recleaned the carb, tried disconnecting the TPS, adjsuting the ap pump, and even put in a new air cleaner, same results, huge power failure from the bike. It would at least stay lit when when it idled on the stand. I used stock jetting, from the manual, ( 05 yz 450). Thinking then it could be an electrical problem, I noticed the neutral wire and the wire harness that goes to the CDI magneto into the motor melted. The iInsullation was melted away from one of the wires, and it was touching the head pipe directly from the motor. Could grounding be a problem? I am going to change, (fix) the wires to see if it alieviates the power loss. Does anyone have any suggestions, or input on the matter. When the bike is moving, I need to give it a lot of clutch and gas to keep the bike going. Even going down a hill, the bike wants to stall. I am running out of ideas.

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I noticed the neutral wire and the wire harness that goes to the CDI magneto into the motor melted. The iInsullation was melted away from one of the wires, and it was touching the head pipe directly from the motor. Could grounding be a problem?
Yes. The way it works, the neutral switch grounds that lead in neutral only. That tells the CDI to lower the rev limit to about 6-7000 rpm, and retard the ignition timing. In addition to the retarded base timing, there is hardly any advance in this mode as engine speed increases. Riding that way would be disappointing to say the least.

You can try cutting off and insulating the wire coming from the CDI first, which will put the bike permanently (until repaired) in the "in gear" mode, where at least that part of the system should then be normal. If that's the problem, it should run right then.

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Yes. The way it works, the neutral switch grounds that lead in neutral only. That tells the CDI to lower the rev limit to about 6-7000 rpm, and retard the ignition timing. In addition to the retarded base timing, there is hardly any advance in this mode as engine speed increases. Riding that way would be disappointing to say the least.

You can try cutting off and insulating the wire coming from the CDI first, which will put the bike permanently (until repaired) in the "in gear" mode, where at least that part of the system should then be normal. If that's the problem, it should run right then.

Gray I think you nailed it!

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The wires were the problem. I was going to buy new wires until I found out it would have been around $300 for those wires. I just repaired them and routed them on the left side of the bike, ( where they are susposed to be) and now the bike runs like a champ. I wonder how much a shop would charge of a repair like that. It took me a while to diagnose the problem.

Next step is to jet it properly, because it is all messed up now. I think I tried compensating too much for the groundout. At least it runs like a champ now.

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