Yeah, just did the top end on my YZ and having similar knocking sounds at low rpm. New cylinder from Cylinder Works and Vertex piston. I uploaded a video of the sound on my channel.
I had something similar to this on an rmx250. It turns out that the head gasket was protruding into the cylinder(the bike about 270cc), making the squish gap disapear, and causing pre-ignition at part throttle.
How much riding with this issue is enough to cause damage? My Cr250 is doing the same thing at mid throttle under heavy load (only on certain straights) and I put 2 hrs in that day. Is it worth worrying about tearing apart or just richen and wait until my next top end which will be soon?
@@ethanreis8465 yea I looked at my piston through the exhaust port and saw a fine dust above my piston rings (definitely causing damage). When I did the top end, I noticed that the previous owner modded the cylinder for more compression which was causing the pinging. I ran race gas for a season instead of getting the head/dome cut to lower compression. I actually just sold the bike and got an EFI 450 so I guess I took the easy way out 😅
@@perfecthips Sure! How's it running? A major thing on these bikes is getting the power smoothed out a bit. Needs to run smooth off idle and have a usable hit, not too explosive. Stock they can explode in the midrange in a way that just makes wheelspin in the woods. I run a low compression head with tight squish, ignition retarded about 2 degrees, and the suzuki needle. All that helps make the power very good in the woods. A lot of guys like a flywheel weight, too, but I haven't been running one lately. My brother and I will do some followup videos while we get his new bike setup!
@@singletrackmarc819ethanol free pump gas Jetting notes: 48 pilot, 165 main, NECJ 3 (suzuki needle), 50 power jet, stock #7 slide. Colorado settings: 42/162, needle one clip if necessary. Have also run 168 main or 45 pilot depending on conditions. Was the TC2 used? That style spark arrestor can plug up with carbon and give issues. But if it revs out clean that wouldn't be it. Maybe just running richer or leaner with the muffler change? Could swap back to see if it's the muffler or not. Look at the plug to see if it is the right color. Grain of sand in the pilot circuit would do it too.
@@singletrackmarc819 keep in mind that changing the needle, especially changing to a different style (2 taper -> 3 taper) would require a pilot and main change as well. Just search for the needle chart or look on thumpertalk
Matt Ellermets haha, yeah I know you guys aren’t dumb. You took the head off? I guess that’s what makes 2 strokes so nice. To me that just a whole other day, I don’t have the capacity to do it in one day lol
@@LukeBrinkerhoff Brian's method: just take the plug out and stick the solder down to the edge of the head from there. Of course that only measures one side, but great way to spot check it on a new-to-you bike!
I can hear it and start with the pilot, then raise the needle one notch. Kind of cool to see you out again riding after a winter like we had.
Am I the only one that really likes the aggressive feel of the stock yz in the woods?
I know this is old…. But nope! Love that sht!
Yeah, just did the top end on my YZ and having similar knocking sounds at low rpm. New cylinder from Cylinder Works and Vertex piston. I uploaded a video of the sound on my channel.
That thread the needle mate had me squeezing my nads
:D when's that in vid? 6:40?
😁
I had something similar to this on an rmx250. It turns out that the head gasket was protruding into the cylinder(the bike about 270cc), making the squish gap disapear, and causing pre-ignition at part throttle.
Did carb adjustment fix this ?
I have a 2003 kx250 with 4.1 hours on the meter after a full engine rebuild new crank and all. It's got a pinging noise in the high rpms
Nothing like the noise of that one tho it's just sounds like a high pitched fast rattle
What's the squish set to? Compression ratio? Fuel?
Mine does the same thing
How much riding with this issue is enough to cause damage? My Cr250 is doing the same thing at mid throttle under heavy load (only on certain straights) and I put 2 hrs in that day. Is it worth worrying about tearing apart or just richen and wait until my next top end which will be soon?
did you ever get an answer? mines doing the same thing
@@ethanreis8465 yea I looked at my piston through the exhaust port and saw a fine dust above my piston rings (definitely causing damage). When I did the top end, I noticed that the previous owner modded the cylinder for more compression which was causing the pinging. I ran race gas for a season instead of getting the head/dome cut to lower compression. I actually just sold the bike and got an EFI 450 so I guess I took the easy way out 😅
i have the same issue when i changed the piston. how did you fix yours?
I think he did a top end and cut the head to give lower compression and tighter squish.
Is that a jday number sticker on his helmet? Where you guys located?
We are in Central Illinois. Local races for us means d17 hs, IXCR, mwxc, crossroads, etcetera. Not sure what his sticker is from
Do these yz250 make good woods bikes?
Yes definitely!
@@MattEllermets what would you add to it? Skid plate and bark busters and I'm good to go?
@@perfecthips Sure! How's it running? A major thing on these bikes is getting the power smoothed out a bit. Needs to run smooth off idle and have a usable hit, not too explosive. Stock they can explode in the midrange in a way that just makes wheelspin in the woods. I run a low compression head with tight squish, ignition retarded about 2 degrees, and the suzuki needle. All that helps make the power very good in the woods. A lot of guys like a flywheel weight, too, but I haven't been running one lately. My brother and I will do some followup videos while we get his new bike setup!
@@singletrackmarc819ethanol free pump gas
Jetting notes: 48 pilot, 165 main, NECJ 3 (suzuki needle), 50 power jet, stock #7 slide. Colorado settings: 42/162, needle one clip if necessary. Have also run 168 main or 45 pilot depending on conditions.
Was the TC2 used? That style spark arrestor can plug up with carbon and give issues. But if it revs out clean that wouldn't be it.
Maybe just running richer or leaner with the muffler change? Could swap back to see if it's the muffler or not.
Look at the plug to see if it is the right color.
Grain of sand in the pilot circuit would do it too.
@@singletrackmarc819 keep in mind that changing the needle, especially changing to a different style (2 taper -> 3 taper) would require a pilot and main change as well. Just search for the needle chart or look on thumpertalk
“Yeah, well let’s just keep riding it” 😂 so did Brian get a bike? I didn’t think you had 2 250s
Oh. “I’m so glad Brian got a bike”
Well off camera we adjusted air screw and measured squish and etc 😁 Yep Brian got an 07
Matt Ellermets haha, yeah I know you guys aren’t dumb. You took the head off? I guess that’s what makes 2 strokes so nice. To me that just a whole other day, I don’t have the capacity to do it in one day lol
@@LukeBrinkerhoff Brian's method: just take the plug out and stick the solder down to the edge of the head from there. Of course that only measures one side, but great way to spot check it on a new-to-you bike!
Matt Ellermets I thought squish test were more of outside measurement?
Idk what to do with it
so you did not even play w the carb thanks
We did, chased tail a bit. Then rebuilt top end, set squish properly and some porting and head work. It wound up an awesome running bike
@@MattEllermetsdid u need race fuel?