Is this just how 2 strokes are??

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8/13/2014 10:00 AM

So as you guys may already know, I switched from a 450 to a 125 this month.. I took it out for the first time yesterday and it was a BLAST. I don't know if I was fast on it but I certainly felt like I was. I also sounded like it too. Sick. Anyway, The bike (05 YZ125) starts with 1-2 kicks everytime when cold, and idles perfectly (maybe even a tiny bit high). But if in between motos I kill the bike and bench race or take a break, when the motor is warm and I come to start it, it takes 5-6 kicks and idles SUPER SUPER low until I bring the revs up, then it idles fine.

Does this sound like a top end deal? Or is this how two strokes operate? I always thought it was the 4strokes that were harder to start when warm.. though I never experienced that with my Fuel Injected 450.

Any thoughts??

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8/13/2014 10:08 AM

Sounds like it may be a little flooded. The float needle and seat might not be sealing completely. Try turning the gas off each time you take a break. If this solves the problem then you have narrowed it down to the float needle and seat.

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Bret Bonham

8/13/2014 10:14 AM
Edited Date/Time: 8/13/2014 10:16 AM

2 strokes should always start easy. My bike is 1 kick almost everytime hot or cold. What is your jetting and premix ratio? What type of fuel are you running? Also color of plug?

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8/13/2014 10:15 AM

Bret wrote:

Sounds like it may be a little flooded. The float needle and seat might not be sealing completely. Try turning the gas off each time you take a break. If this solves the problem then you have narrowed it down to the float needle and seat.

That's actually a great thought Brett.. Could I try testing this also by opening the throttle while kicking it to create a leaner condition?

Is it not wanting to easily start when warm indicative of a top end job needing to be done soon? What are the chances this is due to the bottom end? At this point I'm trying to decide if I should cut my losses and sell it or just hook up the motor and have a solid bike. I want to have a 125 that I can ride as my primary bike.

Also one more question, I seem to be hitting neutral when downshifting from second to first too many times for it to be user error.. Even a buddy that spun a lap on my bike yesterday hit that problem when he was only on the bike for 3 minutes. I know the 05 has a faulty shift stopper so I just replaced that last weekend.. do you think some of the bearings from the broken shift stopper are caught between neutral and first gear? I didn't see any bearings in the clutch basket or when I drained the oil but I just bought the bike so I don't know if they drained out when the last owner had it..


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8/13/2014 10:17 AM

YZ125H1 wrote:

2 strokes should always start easy. My bike is 1 kick almost everytime hot or cold. What is your jetting and premix ratio? What type of fuel are you running? Also color of plug?

I see you're in beverly hills.. I'll need to holler at you when i'm out next. It's still running whatever premix the PO was using, which he said was 32:1 maxima... but you know how craigslist guys are, he hasn't texted me back answers to my questions since he unloaded the bike on me. I haven't accused him of anything just wanted to know if he had any thoughts on the problems.


Would this affect the bike when it's warm? Because it seems to be working fine when it's cold but when warm we're talking a different story.

Thanks brah

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8/13/2014 10:24 AM

YZ125H1 wrote:

2 strokes should always start easy. My bike is 1 kick almost everytime hot or cold. What is your jetting and premix ratio? What type of fuel are you running? Also color of plug?

HazemG wrote:

I see you're in beverly hills.. I'll need to holler at you when i'm out next. It's still running whatever premix the PO was using, which he said was 32:1 maxima... but you know how craigslist guys are, he hasn't texted me back answers to my questions since he unloaded the bike on me. I haven't accused him of anything just wanted to know if he had any thoughts on the problems.


Would this affect the bike when it's warm? Because it seems to be working fine when it's cold but when warm we're talking a different story.

Thanks brah

Did the PO owner say when the topend was last done?

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8/13/2014 10:30 AM

Bret wrote:

Sounds like it may be a little flooded. The float needle and seat might not be sealing completely. Try turning the gas off each time you take a break. If this solves the problem then you have narrowed it down to the float needle and seat.

My thoughts as well.

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If it ain't yer's don't take it, If it ain't the truth dont say it, If it ain't right don't do it...Marcus Aurelius

8/13/2014 10:32 AM

YZ125H1 wrote:

2 strokes should always start easy. My bike is 1 kick almost everytime hot or cold. What is your jetting and premix ratio? What type of fuel are you running? Also color of plug?

HazemG wrote:

I see you're in beverly hills.. I'll need to holler at you when i'm out next. It's still running whatever premix the PO was using, which he said was 32:1 maxima... but you know how craigslist guys are, he hasn't texted me back answers to my questions since he unloaded the bike on me. I haven't accused him of anything just wanted to know if he had any thoughts on the problems.


Would this affect the bike when it's warm? Because it seems to be working fine when it's cold but when warm we're talking a different story.

Thanks brah

YZ125H1 wrote:

Did the PO owner say when the topend was last done?

He said 5 hours ago, but he also said the bike had a rekluse clutch in it (which I did not want but he revealed this to me after a 4 hour trip to pick up the bike) but when I opened up the clutch basket, it looked like a stock clutch to me. I don't really trust the PO.

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8/13/2014 10:36 AM

are you pulling the choke lever to start it after you let it sit?

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8/13/2014 10:38 AM

When you're kicking the bike, are you giving it any gas at all? I was taught not to touch the throttle on a 4 stroke while kicking it (which I normally did anyways). But when I switched, I was told that 2 strokes like a little gas when you're kicking it. When I start mine, as I kick, I twist the throttle a quarter of a turn or so. The bike seems to love it. Not sure if that's right or wrong but it's worked for me.

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8/13/2014 10:41 AM
Edited Date/Time: 8/13/2014 10:44 AM

HazemG wrote:

He said 5 hours ago, but he also said the bike had a rekluse clutch in it (which I did not want but he revealed this to me after a 4 hour trip to pick up the bike) but when I opened up the clutch basket, it looked like a stock clutch to me. I don't really trust the PO.

Well go with what the others have said checking out the float needle and seat it is a good place to start. I also turn my throttle about 1/4 turn when kicking the bike over warm. The only real other problems I have experienced was water in my fuel. Which you can pretty much rule out since the bike was definitely bog when you try to get on it.

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8/13/2014 10:44 AM

IWreckALot wrote:

When you're kicking the bike, are you giving it any gas at all? I was taught not to touch the throttle on a 4 stroke while kicking it (which I normally did anyways). But when I switched, I was told that 2 strokes like a little gas when you're kicking it. When I start mine, as I kick, I twist the throttle a quarter of a turn or so. The bike seems to love it. Not sure if that's right or wrong but it's worked for me.

Not at all.. Like you, on my honda 450 I just kick it and within 1-2 kicks it fires right up, cold, warm whatever.. So have you tried not giving it gas on your 2stroke? Maybe that's what is going on.. I'll give that a shot and see if it helps...


And mxrose, I'm not touching the choke lever at all, cold, warm or otherwise

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8/13/2014 10:45 AM

On my YZ144 I have to crack the throttle a tiny bit when starting warm/hot. It will start 1st kick every time.

Honestly if I just bought a used 125, I would plan on doing a top end with a good quality piston right away. You really don't know the condition of the motor till you tear it down and take a look around. You can check for any rod play at the same time. I did not do this when I bought my 125 and ended up with a shattered piston that left be stranded away from the truck. That's why its a 144 now.

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8/13/2014 10:48 AM

IWreckALot wrote:

When you're kicking the bike, are you giving it any gas at all? I was taught not to touch the throttle on a 4 stroke while kicking it (which I normally did anyways). But when I switched, I was told that 2 strokes like a little gas when you're kicking it. When I start mine, as I kick, I twist the throttle a quarter of a turn or so. The bike seems to love it. Not sure if that's right or wrong but it's worked for me.

HazemG wrote:

Not at all.. Like you, on my honda 450 I just kick it and within 1-2 kicks it fires right up, cold, warm whatever.. So have you tried not giving it gas on your 2stroke? Maybe that's what is going on.. I'll give that a shot and see if it helps...


And mxrose, I'm not touching the choke lever at all, cold, warm or otherwise

Choke lever should at least be pulled when the bike is cold. Also if it has sat and cooled off for an hour or more.

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8/13/2014 10:50 AM

Couple thoughts.

You should never have to use 1st on an MX track. If you feel you need 1st gear, you either need to carry more momentum in the turns or get lower gearing. For reference, stock is 13/48. Make sure someone didn't put something weird on there.

When you removed the old shift stopper, was the bearing still intact? Where the balls and outer race still on it? If not, then those balls went somewhere in the tranny and that certainly won't help anything.

First thing I would do is ditch whatever fuel is in it and start over with a known good reference point. Get some fresh premum pump gas or low grade race fuel if you can find it and mix it 32:1 with a quality oil. Lots of people have good luck with Yamalube-R or Maxima Super-M in these bikes. Then I would open the carb, clean everything and make note of what jetting is in it. Stock pilot is 40 and stock main is 410 and the stock jetting is very close to perfect on these. Make sure some previous owner didn't jack something in there. While the carb is off, I would pull the reed block and inspect the reeds for chips or cracks.

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Powerband in every gear !

8/13/2014 10:50 AM

luckyguy19 wrote:

On my YZ144 I have to crack the throttle a tiny bit when starting warm/hot. It will start 1st kick every time.

Honestly if I just bought a used 125, I would plan on doing a top end with a good quality piston right away. You really don't know the condition of the motor till you tear it down and take a look around. You can check for any rod play at the same time. I did not do this when I bought my 125 and ended up with a shattered piston that left be stranded away from the truck. That's why its a 144 now.

Lol at the last sentence. Makes sense though. So you guys would just repair this one rather than sell it and try to find one in the $3k neighboorhood that might have a motor in better shape? Do you think a top end job would be sufficient or would I have to look into a bottom end as well? The only other thing that sketches me out is the following:

Hitting neutral when downshifting from second to first.. changed the original shift stopper that had broken off, problem ensued. Thinking there may be some bearings stuck somewhere in the gearbox??? Knowing this information, would you still say it is worth rebuilding?


I was super pumped on having a 125 that is strong and reliable.. I understand there is some level of rolling the dice when purchasing a used bike, so what's to say I don't buy another bike that needs a rebuild.. but I just want to know that I won't be tossing countless wads of cash on a 9 year old YZ. I know they are virtually unchanged, but I don't want to spend more than $500 repairing this motor to be in tip top shape.. achievable???

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8/13/2014 10:53 AM

FGR01 wrote:

Couple thoughts.

You should never have to use 1st on an MX track. If you feel you need 1st gear, you either need to carry more momentum in the turns or get lower gearing. For reference, stock is 13/48. Make sure someone didn't put something weird on there.

When you removed the old shift stopper, was the bearing still intact? Where the balls and outer race still on it? If not, then those balls went somewhere in the tranny and that certainly won't help anything.

First thing I would do is ditch whatever fuel is in it and start over with a known good reference point. Get some fresh premum pump gas or low grade race fuel if you can find it and mix it 32:1 with a quality oil. Lots of people have good luck with Yamalube-R or Maxima Super-M in these bikes. Then I would open the carb, clean everything and make note of what jetting is in it. Stock pilot is 40 and stock main is 410 and the stock jetting is very close to perfect on these. Make sure some previous owner didn't jack something in there. While the carb is off, I would pull the reed block and inspect the reeds for chips or cracks.

I defintely hear you on first gear.. Never should need it on a 125 on track. It happened when getting off the track.. but the problem remains that there is an issue there.

When I replaced the shift stopper, it was broken with no visible bearings. I didn't see any when I drained the oil... I am now led to believe they are in the transmission.. what does this mean for me? How much damage (monetarily speaking $$) are we talking? Scrap this bike and just get a different one?


You guys are super helpful.

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8/13/2014 11:00 AM

I would have gotten a 2006 or newer YZ125 just for the better stock suspension. If I was splitting the motor to check for shrapnel I would put in a new crank and send the jug to Eric Gorr to be ported and bored to a 144. You'd have a bullet proof motor for around $800. One thing better than a YZ125 is a YZ144. Same bike with a better spread of power.

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8/13/2014 11:01 AM
Edited Date/Time: 8/13/2014 11:04 AM

You might want to split the cases and see if there is any damage to the transmission from the shifter stop bearing. Cause if you continue to ride it you could risk locking up the motor causing more damage.

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8/13/2014 11:02 AM

IWreckALot wrote:

When you're kicking the bike, are you giving it any gas at all? I was taught not to touch the throttle on a 4 stroke while kicking it (which I normally did anyways). But when I switched, I was told that 2 strokes like a little gas when you're kicking it. When I start mine, as I kick, I twist the throttle a quarter of a turn or so. The bike seems to love it. Not sure if that's right or wrong but it's worked for me.

HazemG wrote:

Not at all.. Like you, on my honda 450 I just kick it and within 1-2 kicks it fires right up, cold, warm whatever.. So have you tried not giving it gas on your 2stroke? Maybe that's what is going on.. I'll give that a shot and see if it helps...


And mxrose, I'm not touching the choke lever at all, cold, warm or otherwise

I tried kicking it a few times without twisting the throttle with mixed results. It would fire sometimes and sometimes not. I'd say give that a shot and see how it does.

Given the way the previous owner is acting, I'd probably put in a good piston and rings as was suggested by someone else just to be safe. I know nothing about bottom ends except I've never had a problem with one.

And for a reference, I've been running a fuel mix of 50% 100LL (get it from a local semi-private airport) and 50% premium gas. Mix that with a 32:1 Bel Ray oil. Bike seems to love this mix. Getting the 100LL is a bit of a pain in the ass but I'm not going to change that for now.

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8/13/2014 11:03 AM

the bike takes a few more kicks when its warm and youre jumping to conclusion that the engine may be on its way out or that you made a bad decision buying the bike....why?
sounds like a jetting/carb issue that everyone has already said, so try their advice and calm down a bit. lol.
125 top ends are so cheap i would have been ordering parts right when that thing rolled into my garage. you dont know how someone rode that bike last, its cheap insurance.

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-'09 KX500AF

- '19 KX450F

8/13/2014 11:05 AM

If that bearing was gone on the stopper, that means it came apart and went through the tranny. The only right way to fix it is to split the cases, inspect everything (gears, shafts, bearings, etc) and replace anything that shows signs of damage.

The half-assed way to "fix" it is to only remove the right side cover and fish out whatever bits you can see. The problem is you can't get at the tranny, especially the countershaft bearing and the blind bearing on the left end of the main shaft.

Read the threads about this on Thumpertalk. Lots of information and pictures.

http://www.thumpertalk.com/topic/512858-replace-your-shift-stopper/

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Powerband in every gear !

8/13/2014 11:09 AM

You dont want a 2stroke to idel more than about 3 to 5 seconds.

If you are not opening the throttle any and just kicking it that is the problem.

Open the throttle half way and kick. It is not like a 4 stroke,it wont flood.

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8/13/2014 11:11 AM

FGR01 wrote:

If that bearing was gone on the stopper, that means it came apart and went through the tranny. The only right way to fix it is to split the cases, inspect everything (gears, shafts, bearings, etc) and replace anything that shows signs of damage.

The half-assed way to "fix" it is to only remove the right side cover and fish out whatever bits you can see. The problem is you can't get at the tranny, especially the countershaft bearing and the blind bearing on the left end of the main shaft.

Read the threads about this on Thumpertalk. Lots of information and pictures.

http://www.thumpertalk.com/topic/512858-replace-your-shift-stopper/

Thanks for the helpful info. Keep in mind I need to add this to the cost of a top end, etc. so it seems like it is going to get pricey fast.. .It sounds as though that is what happened, that the bearings have gone into the tranny. I'm not too familiar with pricing of all this, what would you say this is going to cost?

You sound like you have experience with this issue... your honest opinion on selling/keeping the bike? Any harm to ride it in the meantime? I have a practice day on Sunday I was hoping to ride at.

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8/13/2014 11:12 AM

JBernard_401 wrote:

the bike takes a few more kicks when its warm and youre jumping to conclusion that the engine may be on its way out or that you made a bad decision buying the bike....why?
sounds like a jetting/carb issue that everyone has already said, so try their advice and calm down a bit. lol.
125 top ends are so cheap i would have been ordering parts right when that thing rolled into my garage. you dont know how someone rode that bike last, its cheap insurance.

I understand, the shifting issue is the one that is sketching me out moreso than the warm start deal. I planned on a top end, but not a bottom end and new transmission/splitting the cases.

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8/13/2014 11:26 AM

A compression test is a quick way to determine the general condition of the top end. Some service manuals give an acceptable operating range of 130 psi to 200 psi. If yours is below 150 I would definitely consider replacing the piston and ring(s).

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Bret Bonham

8/13/2014 11:36 AM

Yamaha should have recalled the 05' - 06' YZ125 for that shifter stopper issue, but they didn't. They just updated the part and went on their merry way.
I had one go out in my son's 125 that year, and fortunately it didn't do any damage to the transmission. Replaced it with the new part # and it was great after that. Guess I was lucky.

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8/13/2014 12:43 PM

Sounds like I'm going ot have to split the cases.. not really what I wanted to do on a bike I just purchased...

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8/13/2014 12:54 PM

HazemG wrote:

Thanks for the helpful info. Keep in mind I need to add this to the cost of a top end, etc. so it seems like it is going to get pricey fast.. .It sounds as though that is what happened, that the bearings have gone into the tranny. I'm not too familiar with pricing of all this, what would you say this is going to cost?

You sound like you have experience with this issue... your honest opinion on selling/keeping the bike? Any harm to ride it in the meantime? I have a practice day on Sunday I was hoping to ride at.

I have a 2006. I replaced my shift stopper before it came apart.

Honestly, if it was me I would split the cases and do it right. But that's based on my personal situation of being able to do it myself and not being too worried about paying for whatever parts I might need. Your situation might differ and the cost of repairs or parts might be a bigger factor in your situation.

However, I would feel bad about selling the bike to someone knowing the tranny is already messed up and could potential get worse as debris moves around in there or even cause an accident if it was to lock up or let loose at the wrong time. So, I would either fix it before selling or be sure to let the new owner know what they were buying.

Read through that thread and it will tell you everything you need to know about the shift stopper. Then you can make your own decision.

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Powerband in every gear !

8/13/2014 12:56 PM

Keep the bike. Do the work yourself. Buy a repair manual, case-splitting tool and crank installer tool. Get a new crank and piston. Your shifting issue is likely being caused by either notches in your clutch basket or worn grooves in your shift drum. You will need to split the cases in order to inspect the shift drum - while you are at it you may as well put in your fresh crank and piston. You should be able to make that 125 strong and reliable and stay pretty close to your $500 budget...

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