Jump to content
Sign in to follow this  

YZ125 bogging issues after full rebuild and V-force reed installation

Recommended Posts

Hey fellow 2 stroke lovers, I recently had my YZ125 in the shop for a full rebuild and had them put v-force reeds on while they were at it. I followed the break in procedure and the bike seemed to be running perfect. A week later I took it to the track and it rode flawlessly for the first lap but once it got warmed up it started bogging on me in the higher RPMs. I tried playing with my oil and gas ratio a little bit, using 32:1, 40:1 and 44:1 but it was the same with each ratio, runs perfect for the first lap and then starts bogging. The bogging seems to come after it warms up because if I take it off the track and let it cool off it runs good again for 1 lap. Now I am thinking I need to change the jetting or maybe the new spark plug it has is faulty. Unfortunately I don't know what size jets it has right now, I will find out soon and update this post letting you guys know. I live in the U.A.E. so I am riding in 70-100 degree weather at sea level and high humidity some of the time. I know these factors can effect jetting. I have no idea whats wrong I'm just taking an educated guess that its the jetting, please offer any ideas or thoughts you guys have. Oh and my bike NEVER had bogging issues before the rebuild.

 

Thank you

Charlie

Edited by kx100rider911

Share this post


Link to post
Share on other sites

Loosen the gas cap when it starts to do it and see if it stops. Could be a plugged up vent line on tank. If it runs ok for the first lap that would probably equate to a bowl full (roughly) of gas.

Sounds like gas cap or restrictive fuel flow.

You might take gas line off at carb and see how fast the gas come out when turned on.

  • Like 3

Share this post


Link to post
Share on other sites

Mine bogged after warming up to. I had to bump up to a 440 main jet to get rid of it. 

Share this post


Link to post
Share on other sites

Did you install V-force reeds too?

 

Nope I didn't, could be an airleak at the intake. If it doesn't idle higher after warming up its most likely not an air leak and just the jetting.

Share this post


Link to post
Share on other sites

I would go over the carb lines first. Make sure that there is proper fuel flow. Check the gas cap, and the hose on the top of it. Also, check the filter in the petcock. If a new main doesn't help, definitely give it a good cleaning.  If there isn't enough flow... it will bog in the top end. 

Share this post


Link to post
Share on other sites

I would go over the carb lines first. Make sure that there is proper fuel flow. Check the gas cap, and the hose on the top of it. Also, check the filter in the petcock. If a new main doesn't help, definitely give it a good cleaning.  If there isn't enough flow... it will bog in the top end. 

 

Nope I didn't, could be an airleak at the intake. If it doesn't idle higher after warming up its most likely not an air leak and just the jetting.

 

Ok thanks for the replies guys, a guy at the track said that it was idling pretty high so it might be an air leak. the fuel seems to be flowing fine out of the tank but i will check the petcock filter in case. Do you guys think I should try a 420 main? maybe a 430? stock is 410 and thats what it has right now. The guy who rebuilt it told me he cleaned the carb, I hope he did.

Share this post


Link to post
Share on other sites

Did the guy who rebuilt it do a leak down check? If not stop riding it and do it. I learned the hard way. I am under the strict belief that you can have NO air leak on a 2T. Now you can compensate for an air leak with going to a richer main, which I have done, but that is a band aid fix. Good luck

P.S. Even when I do a top end only I still do a leak down check for piece of mind.

Share this post


Link to post
Share on other sites

Ok thanks for the replies guys, a guy at the track said that it was idling pretty high so it might be an air leak. the fuel seems to be flowing fine out of the tank but i will check the petcock filter in case. Do you guys think I should try a 420 main? maybe a 430? stock is 410 and thats what it has right now. The guy who rebuilt it told me he cleaned the carb, I hope he did.

You could try to go richer on the main, but do it one step at a time. 420, then 430. I have my doubts on the main but it is worth a shot.

Share this post


Link to post
Share on other sites

Like stated above I would not ride this until you do a leak down test. I just made one last week for under $20 per the honda forum sticky.

This issue sounds like a typical air leak. You can try carb cleaner but the only way to know is to build a tester. Afte this you will know the condition I crank seals, base gasket, reed gaskets and so on. Definitely a must

  • Like 1

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×