Ok. I have a 96 YZ125 right now. It has Pro series carbon fiber reeds, fmf gold series fatty with power core II silencer with new packing, tmx carborator. I just put a new top end in it. Ever since i bought it i have had no power in the bike. I thought it just needed a rebuild but it didn't seem to help. I watch other 125s and find that they how so much more power than mine. You would think that with all the mods i have put into it that it would gain some power somewhere. It is kind of depressing to see other bikes riding by on wheelies and mine having trouble getting up in second. The only way i can get it up in second is by popping it in second.:ugg: I have ridden some other bikes and the power just rips mine to shreds. I would like to know what is wrong. Is my bike just too worn out or something? What can i do to fix my problem?
Bike has no power
- Thread starter YZ kid
- Start date
Could be a lot of things
Air leak in the intake, power valve not operating, timing off, BAD GAS/OLD GAS, carb not properly jetted, piston installed backwards,etc etc.. Did you install all the mods yourself? Does it develop power at any RPM? Have you ridden another 96, like yours for comparison? What size tire is on the rear? All or any of those things need to be resoved.
Air leak in the intake, power valve not operating, timing off, BAD GAS/OLD GAS, carb not properly jetted, piston installed backwards,etc etc.. Did you install all the mods yourself? Does it develop power at any RPM? Have you ridden another 96, like yours for comparison? What size tire is on the rear? All or any of those things need to be resoved.
marcusgunby
LIFETIME SPONSOR
- Jan 9, 2000
- 6,450
- 2
im thinking powervalve not working.
S
Saratoga
If you have never cleaned the power valves then this would be the first thing to do. On most bikes you can remove the power valve cover and watch it turn as you rev the bike in idle. If the valves are stuck in one position, power will be way down just like you described. Do not waste time wondering or asking everyone how to do this. Go buy a manual and start maintaining your bike to get optimum performance.
BillyWho
Sir-Breaks-Alot
- Mar 22, 2001
- 1,828
- 0
My first guess would be this also. One way to test if it is the power valve, is to ride it a bit , then come in and take the cover off and disconnect the power valve arm, put the cover back on, and ride it the same way you just did. You should notice an incredible loss of power, if not then you know it has some thing to do with the valve.
I have the same bike and even at 122 psi the thing still screams. When you put the new top end on it did you clean the power valve set up? If you don't even know how to do a compression test then why did you do the top end? Anyway, start with the power valve, DO a comp test so you have a baseline for future ref. Dump ALL the fuel, change the oil in the tranny, set your carb to stock settings, check your reed set up, CLEAN and OIL a NEW filter, and buy good gas and pre-mix. Once you have the motor right, change your gearing: either a 12 tooth or a 52 rear, not both.
B]Ever since i bought it i have had no power in the bike.[/B] Then why did you buy it? I hope you got a steal deal.
Dave
B]Ever since i bought it i have had no power in the bike.[/B] Then why did you buy it? I hope you got a steal deal.
Sell it to me, I'll give you $100.00 you pay shipping;)
Dave
On a 125, we should be lucky to be at 155 - 160 on a new top end, so I’ve now been hearing. I heard the 170 -180 and ripped mine down and sent it to Eric, thinking I was way off the charts. Well it is a good thing I did, the bridge had some scaring. Curious to see what the 133 will have as far as psi. However, I recommend if you are going to do a top end, have a gauge! Check it before you tear down, and check it immediately upon torquing the last head bolt. I went out and bought a second one just to make sure the reading was right. Don’t guess and screw something up by rolling the back tire to start the engine through the transmission.
Mike you should post a thread re: frame hole cleaning. It is a good point
Dave
Mike you should post a thread re: frame hole cleaning. It is a good point
Dave
Checking the compression won’t tell you everything. It is only an indication that something is wearing out. The only way to know for sure if the rings, piston or cylinder is worn is to tear it down and measure it. Until then you are just grasping at straws.
On my 250 the compression new is 210 and I recently checked it and it was 190. You’d think all was well but when I tore it down, the rings and piston were both out of spec and needed to be replaced.
On my 250 the compression new is 210 and I recently checked it and it was 190. You’d think all was well but when I tore it down, the rings and piston were both out of spec and needed to be replaced.
I agree a compression test will not tell you the full story, it is a guide, look at your situation, 210 to 190, that is almost 10 percent. I believe that’s the rule of thumb to use. Without a gauge, all you are doing is guessing.
Dave
Dave
Ok I have the same bike...same problem I found that by adjusting the carb properly and making sure I have the correct ratios ...ie sprocket sizes that I could get it to run great...however slight changes in the sprocket size made noticable differences..also check powervalves...mine were horrible when I finally got around to cleaning them and I noticed a big difference in performance.
Good luck
Vanessa
Good luck
Vanessa
