Yz 125 problem

JR26
Posts
13
Joined
8/31/2018
Location
CA
10/1/2018 7:35pm
I have a 2017 YZ125 with v force reeds and FMF pipe. It’s never given me any trouble jetting is on point idle is too. I was sitting at the gate at one of my races and when it came time to start my bike it wouldn’t. So I pushed it back to the pits and finally got it running but it bogged until it was warm. I put a new plug in. I cleaned the power valve and my piston had 9 hours and still looks good. Think maybe carb?
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Marty1028
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699
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10/5/2017
Location
Frankfort, IN US
Fantasy
1394th
10/1/2018 7:54pm
Shitty gas or clogged air filter. Check the easy stuff first
JR26
Posts
13
Joined
8/31/2018
Location
CA
10/1/2018 7:57pm
Marty1028 wrote:
Shitty gas or clogged air filter. Check the easy stuff first
I change out air filter every ride and gas is premium mixed with VP race gas
2stroked
Posts
185
Joined
10/15/2013
Location
Ontario, CA US
10/2/2018 6:27am
Take your carb off. Remove the float bowl. Check the needle jet to make sure it doesnt have a speck of dirt on it preventing it from seating flush. (sometimes when this happens you just dump fuel out of the bowl while standing still) Also make sure the needle jet isnt grooved. After that check the float tabs arent bent or damaged. Then remove the pilot and main jets, clean them (id just replace with new), then clean all the circuits out of the carb. Reassemble.

Next while you have the carb apart and off the bike, check your vforce reeds and the cage. Did you double gasket and yamabond the gaskets? Vforce reed cages are notorious for not sealing correctly and causing lean conditions. You'll know because the plug reading will be very light almost white. Make sure the reeds are sealing and aren't chipped.

Last, put fresh gas in it. Have you removed your petcock and cleaned the little skinny filter thing at all? Those get gummed up sometimes.
1
Moto96
Posts
670
Joined
8/9/2018
Location
CA
10/2/2018 7:55am
2stroked wrote:
Take your carb off. Remove the float bowl. Check the needle jet to make sure it doesnt have a speck of dirt on it preventing it...
Take your carb off. Remove the float bowl. Check the needle jet to make sure it doesnt have a speck of dirt on it preventing it from seating flush. (sometimes when this happens you just dump fuel out of the bowl while standing still) Also make sure the needle jet isnt grooved. After that check the float tabs arent bent or damaged. Then remove the pilot and main jets, clean them (id just replace with new), then clean all the circuits out of the carb. Reassemble.

Next while you have the carb apart and off the bike, check your vforce reeds and the cage. Did you double gasket and yamabond the gaskets? Vforce reed cages are notorious for not sealing correctly and causing lean conditions. You'll know because the plug reading will be very light almost white. Make sure the reeds are sealing and aren't chipped.

Last, put fresh gas in it. Have you removed your petcock and cleaned the little skinny filter thing at all? Those get gummed up sometimes.
Easier way to check the petcock deal is just pull off the line and turn it on.
Hard starting is usually worn reeds or low compression(once you've checked all the easy stuff like spark and gas.
1

The Shop

10/2/2018 8:31am
9 hours on a top end is probably past due according to the service manual. Not sure if you are super aggressive but I'd get that top end changed.
1
2stroked
Posts
185
Joined
10/15/2013
Location
Ontario, CA US
10/2/2018 2:17pm
2stroked wrote:
Take your carb off. Remove the float bowl. Check the needle jet to make sure it doesnt have a speck of dirt on it preventing it...
Take your carb off. Remove the float bowl. Check the needle jet to make sure it doesnt have a speck of dirt on it preventing it from seating flush. (sometimes when this happens you just dump fuel out of the bowl while standing still) Also make sure the needle jet isnt grooved. After that check the float tabs arent bent or damaged. Then remove the pilot and main jets, clean them (id just replace with new), then clean all the circuits out of the carb. Reassemble.

Next while you have the carb apart and off the bike, check your vforce reeds and the cage. Did you double gasket and yamabond the gaskets? Vforce reed cages are notorious for not sealing correctly and causing lean conditions. You'll know because the plug reading will be very light almost white. Make sure the reeds are sealing and aren't chipped.

Last, put fresh gas in it. Have you removed your petcock and cleaned the little skinny filter thing at all? Those get gummed up sometimes.
Moto96 wrote:
Easier way to check the petcock deal is just pull off the line and turn it on. Hard starting is usually worn reeds or low compression(once...
Easier way to check the petcock deal is just pull off the line and turn it on.
Hard starting is usually worn reeds or low compression(once you've checked all the easy stuff like spark and gas.
Absolutely true. However what you can't determine without removing the petcock is how much lint, grit, sand, is adhered to the filter its self. Ive found that sometimes there are specks of grit in there that bounce around while riding and slow down the fuel flow. Once you stop riding on the tank settles, the speck can dislodge, fall, or become unattached. A small chance yes, but it only costs you a gasket and 5 minutes of time to check.

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