YZ ignition timing

It won't fit if you put the plug in first then put the gauge on after?

You can cut threads down on spark plug to get less hieght, or cut and drill a hole in a piece of steel to mount to head stud, then Buy magnetic base to hold indicator, you should have some type of set screw to hold indicator from moving, once that is done find tdc and set indicator to 0. Rotate flywheel clockwise till indicator reads .007", that should be stock timing, check timing marks on flywheel to stator plate. Loosen 3 screws and line up mark on stator plate to flywheel. Even if your bikes timing is fully retarded it wont feel like a 125, to far advanced and it will likely detonate. Gearing, jetting all have affect on how a bike feels, if you do feel it is timing, get a manual or download one, here is a very good link to yz250 timing. I personally run my bike a little retarded, smoother hit and more traction.
https://thumpertalk.com/forums/topic/584339-yz250-timing-thread/

Kristen_Valentino wrote:

You can cut threads down on spark plug to get less hieght, or cut and drill a hole in a piece of steel to mount to head stud, then Buy magnetic base to hold indicator, you should have some type of set screw to hold indicator from moving, once that is done find tdc and set indicator to 0. Rotate flywheel clockwise till indicator reads .007", that should be stock timing, check timing marks on flywheel to stator plate. Loosen 3 screws and line up mark on stator plate to flywheel. Even if your bikes timing is fully retarded it wont feel like a 125, to far advanced and it will likely detonate. Gearing, jetting all have affect on how a bike feels, if you do feel it is timing, get a manual or download one, here is a very good link to yz250 timing. I personally run my bike a little retarded, smoother hit and more traction.
https://thumpertalk.com/forums/topic/584339-yz250-timing-thread/

good info provided here... If you’re complaining about lack of throttle response/ hit you definitely don’t want to retard your ignition... I’d personally start at the .007” stock timing or maybe .010” BTDC which should be about one degree advanced... if you’re running a good quality octane fuel 1 degree shouldn’t cause you any detonation issues...

Somebody said that Yamaha never developed their YZ250.
Somebody else said you could rebuild a 2005 YZ to be just like a new bike.
All of those people were wrong.

The best you can hope for is to get your YZ working as if it rolled off the showroom. That's a great place to start testing.

mattyhamz2 wrote:

It won't fit if you put the plug in first then put the gauge on after?

Haven’t tried that yet. I was in a hurry to see how it fit before I went to dinner with my parents lol

Kristen_Valentino wrote:

You can cut threads down on spark plug to get less hieght, or cut and drill a hole in a piece of steel to mount to head stud, then Buy magnetic base to hold indicator, you should have some type of set screw to hold indicator from moving, once that is done find tdc and set indicator to 0. Rotate flywheel clockwise till indicator reads .007", that should be stock timing, check timing marks on flywheel to stator plate. Loosen 3 screws and line up mark on stator plate to flywheel. Even if your bikes timing is fully retarded it wont feel like a 125, to far advanced and it will likely detonate. Gearing, jetting all have affect on how a bike feels, if you do feel it is timing, get a manual or download one, here is a very good link to yz250 timing. I personally run my bike a little retarded, smoother hit and more traction.
https://thumpertalk.com/forums/topic/584339-yz250-timing-thread/

I thought about cutting a few threads off for more clearance. And I have a set screw on the side for it also. There is a spacer machined that fits inside the spark plug where the ceramic insulator was so it’s a tight fit. I also have my manual and a Two Stroke engine building boom for reference as well

Kristen_Valentino wrote:

You can cut threads down on spark plug to get less hieght, or cut and drill a hole in a piece of steel to mount to head stud, then Buy magnetic base to hold indicator, you should have some type of set screw to hold indicator from moving, once that is done find tdc and set indicator to 0. Rotate flywheel clockwise till indicator reads .007", that should be stock timing, check timing marks on flywheel to stator plate. Loosen 3 screws and line up mark on stator plate to flywheel. Even if your bikes timing is fully retarded it wont feel like a 125, to far advanced and it will likely detonate. Gearing, jetting all have affect on how a bike feels, if you do feel it is timing, get a manual or download one, here is a very good link to yz250 timing. I personally run my bike a little retarded, smoother hit and more traction.
https://thumpertalk.com/forums/topic/584339-yz250-timing-thread/

Paul_Pitzonka wrote:

good info provided here... If you’re complaining about lack of throttle response/ hit you definitely don’t want to retard your ignition... I’d personally start at the .007” stock timing or maybe .010” BTDC which should be about one degree advanced... if you’re running a good quality octane fuel 1 degree shouldn’t cause you any detonation issues...

I’d like to set it back to stock or slightly advance it to take advantage of the higher octane fuel. And for fuel she drinks C12. I just think I must have set it wrong when I rebuilt it and want it back to how it was

mattyhamz2 wrote:

It won't fit if you put the plug in first then put the gauge on after?

eric513anderson wrote:

Haven’t tried that yet. I was in a hurry to see how it fit before I went to dinner with my parents lol

Ahh gotcha. I'm wondering if that might give you enough clearance

mattyhamz2 wrote:

It won't fit if you put the plug in first then put the gauge on after?

eric513anderson wrote:

Haven’t tried that yet. I was in a hurry to see how it fit before I went to dinner with my parents lol

mattyhamz2 wrote:

Ahh gotcha. I'm wondering if that might give you enough clearance

Close! Still not enough, I’ll have to shave down that spacer some

I have taken a spark plug and just drilled a hole in it for a plastic set screw, then you gain a little room, I made up a setup with spark plug threads and a set screw to hold Indicator, its .750" total length works well.

This is going to sound way ghetto but . . . I took some vynil hose that fit around the dial gauge
and then wedged it into the spark plug hole. That should give you the clearance you need.
No, the gauge did not move at all as observed by mucho shakes and wiggles. Heck, it's
only taking the load of that tiny spring in the gauge so it doesn't take much to hold it still. Worked primo.

Did you take the power valves out when you rebuilt it? Remove the power valve cover that's above the pipe and take a picture of it. Theres a piece that breaks off just about every yz250 power valve. When it does you wont notice it until the piece gets stuck and wont let the power valve close which then kills the bottom end power.

Most of the time you can fish the piece out and it will never have a problem again.

FWYT wrote:

This is going to sound way ghetto but . . . I took some vynil hose that fit around the dial gauge
and then wedged it into the spark plug hole. That should give you the clearance you need.
No, the gauge did not move at all as observed by mucho shakes and wiggles. Heck, it's
only taking the load of that tiny spring in the gauge so it doesn't take much to hold it still. Worked primo.

It’s not ghetto if it works lol

Jterry wrote:

Did you take the power valves out when you rebuilt it? Remove the power valve cover that's above the pipe and take a picture of it. Theres a piece that breaks off just about every yz250 power valve. When it does you wont notice it until the piece gets stuck and wont let the power valve close which then kills the bottom end power.

Most of the time you can fish the piece out and it will never have a problem again.

Yeah I had the power valve assembly out when I sent the cylinder to Powerseal USA to be replated. There was a spring that was broken in there and I replaced it with s new oem one. I’ll have to take the cover off in the next day or so when I get more time

Here's a pic showing what breaks off.

It's a combination of all things , compression, how much leak down past the rings, if the engine is sealed up, which is checked with a different leak down tester. Everything has to b good or it won't pull down low out of the corners. . A rear tire that is 2 chunky , ala 2 much traction will cause a bike 2 b slow out of the corners, and difficult to get off the line. I race a rm250. If you ever hear a 2 stroke that is professionally built you can hear how bad the motor is in the crispness of how it revs up. I am 62. And have been following this sport since 1971. Good luck..

Got the ignition timing set where it needs to be. Had to slightly modify my gauge but that’s fixed now. Bike still feels the same. I feel like if I try to roll into the power I have to wait for it to hit. Bike just feels sluggish. I can’t figure it out. Same jetting I ran before it was rebuilt. 48 pilot, 178 main, & needle on 2nd clip. Plug was a little dark so I might drop the main to a 175 and see if it’s any better. I did take the side power valve cover off and start the bike & rev it. The arm just barely moves. I’d expect it to move a lot more? Maybe the power valve is stuck open? I got a video of it I’ll have to post to my YouTube then link it here

Here’s the spark plug after a quick little play ride. In this picture I’m running the VP c12 mixed 32:1. I could mix it 50/50 with pump gas but didn’t think it would mess with the jetting any since it is not oxygenated. Weird that it still feels the same when I did mix it 50/50 tho

What gearing are you running? Clutch is good? Did you try 3rd clip on the needle, with the fuel your running you could advance timing 2 to 3 degrees

Kristen_Valentino wrote:

What gearing are you running? Clutch is good? Did you try 3rd clip on the needle, with the fuel your running you could advance timing 2 to 3 degrees

Gearing is stock. Clutch is fine. I haven’t messed with the jetting yet. Timing is set to stock but I thought about advancing it some later. I’ll post the video of the power valve arm. I’m almost positive this is what it is

Looks like the powervalve for sure is stuck. More than likely its jammed open causing the loss of bottom end. That pwervalve actuator arm moves at least 10-12mm when it opens. That's your problem for sure.

eric513anderson wrote:

Here’s the spark plug after a quick little play ride. In this picture I’m running the VP c12 mixed 32:1. I could mix it 50/50 with pump gas but didn’t think it would mess with the jetting any since it is not oxygenated. Weird that it still feels the same when I did mix it 50/50 tho

I just had a similar issue with my TMR big bore set up. I had a Boyesen rad valve without a reed spacer (5mm) and the bike was dead on the bottom. It turned out there was not a enough crank case volume to run correctly. I am now running the Vforce with a 5mm spacer and reed gaskets on both sides to give me about 6mm of additional spacer. Motor rips.

The plug looks good.

eric513anderson wrote:

Here’s the spark plug after a quick little play ride. In this picture I’m running the VP c12 mixed 32:1. I could mix it 50/50 with pump gas but didn’t think it would mess with the jetting any since it is not oxygenated. Weird that it still feels the same when I did mix it 50/50 tho

Wycked31 wrote:

I just had a similar issue with my TMR big bore set up. I had a Boyesen rad valve without a reed spacer (5mm) and the bike was dead on the bottom. It turned out there was not a enough crank case volume to run correctly. I am now running the Vforce with a 5mm spacer and reed gaskets on both sides to give me about 6mm of additional spacer. Motor rips.

The plug looks good.

Sorry, just noticed in your picture of the engine there is a reed spacer.

Call Tom Morgan and TMR and pick his brain. He is out of WI.

eric513anderson wrote:

Here’s the spark plug after a quick little play ride. In this picture I’m running the VP c12 mixed 32:1. I could mix it 50/50 with pump gas but didn’t think it would mess with the jetting any since it is not oxygenated. Weird that it still feels the same when I did mix it 50/50 tho

Wycked31 wrote:

I just had a similar issue with my TMR big bore set up. I had a Boyesen rad valve without a reed spacer (5mm) and the bike was dead on the bottom. It turned out there was not a enough crank case volume to run correctly. I am now running the Vforce with a 5mm spacer and reed gaskets on both sides to give me about 6mm of additional spacer. Motor rips.

The plug looks good.

Wycked31 wrote:

Sorry, just noticed in your picture of the engine there is a reed spacer.

Call Tom Morgan and TMR and pick his brain. He is out of WI.

Power valve is stuck if you watch the video I posted. I’m pretty sure I messed something up when I took everything out of the clutch case cover to have it cerakoted. I had some trouble with getting the governor back in and I’m pretty sure that is the cause of it all. Won’t know for sure until I tear into it

Wycked31 wrote:

I just had a similar issue with my TMR big bore set up. I had a Boyesen rad valve without a reed spacer (5mm) and the bike was dead on the bottom. It turned out there was not a enough crank case volume to run correctly. I am now running the Vforce with a 5mm spacer and reed gaskets on both sides to give me about 6mm of additional spacer. Motor rips.

The plug looks good.

Wycked31 wrote:

Sorry, just noticed in your picture of the engine there is a reed spacer.

Call Tom Morgan and TMR and pick his brain. He is out of WI.

eric513anderson wrote:

Power valve is stuck if you watch the video I posted. I’m pretty sure I messed something up when I took everything out of the clutch case cover to have it cerakoted. I had some trouble with getting the governor back in and I’m pretty sure that is the cause of it all. Won’t know for sure until I tear into it

I figured it was something in the governer. If you had posted this on FB I commented that there. I’ve had the pin wear the shaft there and fall out. You lose all actuation of the PV and it floats wherever it wants to. Ball bearings go around the clutch. I chased my tail for weeks until I realized that. If yours was apart that’s the first thing I’d check especially if you said it went together hard.

Wycked31 wrote:

I just had a similar issue with my TMR big bore set up. I had a Boyesen rad valve without a reed spacer (5mm) and the bike was dead on the bottom. It turned out there was not a enough crank case volume to run correctly. I am now running the Vforce with a 5mm spacer and reed gaskets on both sides to give me about 6mm of additional spacer. Motor rips.

The plug looks good.

Wycked31 wrote:

Sorry, just noticed in your picture of the engine there is a reed spacer.

Call Tom Morgan and TMR and pick his brain. He is out of WI.

eric513anderson wrote:

Power valve is stuck if you watch the video I posted. I’m pretty sure I messed something up when I took everything out of the clutch case cover to have it cerakoted. I had some trouble with getting the governor back in and I’m pretty sure that is the cause of it all. Won’t know for sure until I tear into it

I figured it was something in the governer. If you had posted this on FB I commented that there. I’ve had the pin wear the shaft there and fall out. You lose all actuation of the PV and it floats wherever it wants to. Ball bearings go around the clutch. I chased my tail for weeks until I realized that. If yours was apart that’s the first thing I’d check especially if you said it went together hard.

Wycked31 wrote:

Sorry, just noticed in your picture of the engine there is a reed spacer.

Call Tom Morgan and TMR and pick his brain. He is out of WI.

eric513anderson wrote:

Power valve is stuck if you watch the video I posted. I’m pretty sure I messed something up when I took everything out of the clutch case cover to have it cerakoted. I had some trouble with getting the governor back in and I’m pretty sure that is the cause of it all. Won’t know for sure until I tear into it

dmm698 wrote:

I figured it was something in the governer. If you had posted this on FB I commented that there. I’ve had the pin wear the shaft there and fall out. You lose all actuation of the PV and it floats wherever it wants to. Ball bearings go around the clutch. I chased my tail for weeks until I realized that. If yours was apart that’s the first thing I’d check especially if you said it went together hard.

Yeah I’ll have to take that clutch case cover off this weekend if I have time and see what’s going on