2013 yz250 need advice

[bigmendoza2012]

Hello everyone, 

 

I just bought this bike used it's a 2013 yz250, fmf gnarly pipe with a power core 2 exhaust and vforce 3 reeds.  I rode it three hours and spark plug fouled up pretty bad. It's the stock needle n3ew with the clip on the second to top tab. The main jet is 178 and the pilot is a 50. 

I ride only trails and so I'm always at 1/2 to 1/4 throttle. I notice when it fouled I was going down hill for 15 minutes (had it in 5th gear no throttle) and it fouled. I bought this bike because people said it would be a good trails bike. Is it possible to jet it to for my style of riding? I ride very slow and little to no throttle unless Hill climbing. 

 

What would you guys suggest I run in terms of jets??? 

Also my reed valve has a Crack would this affect anything?

 

Thank you. 

[BDubb106]

Replace the reed petals before you mess with jetting. Damaged reeds will give the effect of being rich. 

[bigmendoza2012]

Ok i bought the Boyesen RAD valve, because seemed to be made better. Any suggestions on jetting?? Should I leave it with the stock setting? 

[markmc2]

was your bike idling all the way down for 15 minutes? clutch in or 'engine braking'?

 

the reed thing might fix you up but maybe you also could blip the throttle every once in a while or kill the engine down hill (bump start it before you reach the bottom).

 

around here there ain't no 15 minute long down hills (too flat)!!!

[bigmendoza2012]

The engine was in 5th but just idleing,  meaning I didn't use the clutch. So what I did was just put in 5th gear and used my brakes when I pick up too much speed. 

 

Ya I'm lucky there is a hill close to my house, it's a stead incline for miles.  Also people don't know about it so it's pretty quiet, I'm hoping to get my bike running well so I can to different places. Love the trails. 

[BDubb106]

 I would suggest leaving the jetting alone until you get those fresh reeds installed. 

 

I run 40:1... 175 main, 50 pilot, JD red needle 3rd POS. Adjust A/S as needed. 

[temporarily_locked]

Elevation and temperature? You have all stock jetting, which is good for sea level and around 70 degrees. If you're at a higher elevation, you are going to need to rejet.

[bigmendoza2012]

Sea level to 1,200. Temps been high 70s

Edited November 4, 2015 by bigmendoza2012

[mlatour]

If your local trails only allow using 1/4 throttle most of the time, perhaps a YZ250 isn't the right choice of bike.

 

It will have to be jetted really lean on the pilot and needle circuts not to foul up on a regular basis.

[markmc2]

if you needed zero throttle input for a 15 minute downhill i would say kill it and coast down. sounds like a fun hill. how does the bike handle going up?

[BDubb106]

If your local trails only allow using 1/4 throttle most of the time, perhaps a YZ250 isn't the right choice of bike.

 

It will have to be jetted really lean on the pilot and needle circuts not to foul up on a regular basis.

I can lug my Yz all day long without fouling a plug, I can run it wide open on the track as well. I can't remember the last time I fouled a plug. It's all about set up and making sure jetting is good, fuel quality is good, and your engine is fresh. 

[mlatour]

I can lug my YZ125 down low forever as well as it's jetted as close to "perfect" as possible.

(squish height re-adjusted and pump/race fuel used as well)

 

My point is that even jetted properly, a high strung MX'er isn't the best choice for super slow trail conditions

where a more trail oriented bike can idle / ride slow all day without risk of overheating as well.

Edited November 4, 2015 by mlatour

[BDubb106]

I can lug my YZ125 down low forever as well as it's jetted as close to "perfect" as possible.

(squish height re-adjusted and pump/race fuel used as well)

 

My point is that even jetted properly, a high strung MX'er isn't the best choice for super slow trail conditions

where a more trail oriented bike can idle / ride slow all day without risk of overheating as well.

You only have to worry about that on orange bikes  ?

 

Anyways, you are correct... correcting squish is a must on Yz's. I have never owned one that has not needed the squish corrected from the factory. They cut them to a very "safe" level and I understand why. 

[bigmendoza2012]

That's great because I worried I did wrong bike. I don't want to sell it because I just got it and have less than 4 hours on it. When I get the new reed valve I try to run the bike a little harder. I did see there is a lot of threads about squish but haven't really read about it. I was hoping because it's a new bike I could ride it without touching the engine.

[bigmendoza2012]

if you needed zero throttle input for a 15 minute downhill i would say kill it and coast down. sounds like a fun hill. how does the bike handle going up?

The bike is amazing, it idles perfect, when I climb Hills it never hesitates. I put it in second gear and it climbs anything easy. Seemed to run super strong before fouling the plug. I have never rode anything like it. But I baby it, because it's new to me.

[bigmendoza2012]

Here are some pics of the trail. I really like the bike, but I will have to learn to jet it because I'm not ready to sell it. For the Boyesen do you keep the spacer in? Or do you remove it (the stock spacer). Also do you think the lectron carb would solve all my jetting problems?

Edited November 4, 2015 by bigmendoza2012

[mlatour]

Wow that looks like a nice place to ride!

Those aren't exactly low speed trails I had in mind, there's plenty of room to let it rip once your skills and experience allows.

 

I'm sure that once the reeds are replaced and perhaps the pilot and needle circuits leaned out a bit,

the plug fouling will be issues of the past.

Also consider using a lower flash point premix oil (Lucas, Interceptor etc.) rather than a 'racing' type oil.

 

Having the squish height checked and revised if required will make the engine run even crisper and lessen the chance of detonation

if your jetting is slightly off or fuel's octane a bit low.

 

Just avoid compression braking down long grades, having the engine rev up with the throttle closed isn't good for a 2-stroke

as it relies on the intake charge for cooling and lubrification.

Edited November 4, 2015 by mlatour

[bigmendoza2012]

Update: I just put the Boyesen reed valve, rode for 1 hour pretty hard and when I checked my spark plug, again it was covered in oil. Like the threads on my spark plug had a bunch of dark oil on it. What does this mean? Any suggestions? 

[mlatour]

Even jetted 'perfectly', it's normal for the spark plug threads to accumulate oil.

More importantly, was the firing tip of the plug oily?

 

As I've mentionned in a previous post here (#9 higher up is this discussion)

since you are mostly trail riding, your engine could benefit from slightly leaning out the pilot jet and raising the needle's clip position.

 

Perhaps you've seen it posted before, here's a handy 'how-to' about reading spark plugs:

 

link:   http://www.braigasen.com/howtoread.htm

Edited November 12, 2015 by mlatour