YZ250 Enduro Conversion

In this video I upgrade my YZ250 to make it a bit more enduro and trail friendly. I also share my musings about various topics related to 2 strokes and the YZ250.
Music Credits:
Music from #Uppbeat (free for Creators!):
uppbeat.io/t/a...
License code: SU4UMC3XGY1YMS7P
Music from #Uppbeat (free for Creators!):
uppbeat.io/t/h...
License code: BPDZB4V3XHKPXCBK
Music from #Uppbeat (free for Creators!):
uppbeat.io/t/h...
License code: SK4OTJ0ITXPJDESL

[@theblishknovk]

Acerbis oversized tank eould be nice on that as well as skid plate and some hand guards for trail use. Beautiful bike.

[@dwaynemartin5174]

My yz has a wr400 transmission 13 oz flywheel 2010 wr450 forks shock swing lineage gruly pipe and rekuls clutch it's a ktm killer lol

[@EarthSurferUSA]

It would be nice if a dirt bike magazine today had the staff who knew how to jet a carb and do some back to back pipe tests, to test the kind of power they make on a stock engine. That Lexx pipe first I have ever seen), look like it is made very well, but I suspect because of the slightly shorter tuned length, (by the looks of it), the FMF Gnarley may be tuned for a bit more low end power (longer to the stinger, it looks.). My engine output turned out very nice, with a lot more lower rpm power and seemingly not much top rpm loss (stupid me did not put a tach on it when it was stock.). 1) FMF Gnarley pipe for a lower rpm target 2) V-force reeds with no stock aluminum spacer plate, (Open earlier and stuffs the cases a bit. Allows rear transfer port to flow better with no reed stop in the way as stock has). 3) Lower the cylinder by not using a cylinder base gasket. Use a great sealer. You don't want any leaks there, (3M Nitrile rubber and gasket adhesive #847, brown, is great stuff.). The lower cylinder lowers the exhaust port time area to better match the lower rpm pipe target. More compression does require 100 octane gas. 4) lean the jetting out. Stock bike is super rich. Higher compression cleaned it up quite a bit. Still going leaner, with the needle clip down a half groove. Need to go further, then tune for the main jet with full throttle runs. Man,--this bike is sold running super rich. Oil droplets o the backs of my jersey's. There is probably 2-3hp by just cleaning up the jetting alone. There should be no oily spooge exiting your pipe, let alone droplets from the silencer to your jersey. Still pretty smooth, but strong power from the crack of the throttle, (will not need a flywheel weight for my riding). So much easier to loft the front end over stuff at low rpm's, and shot shifts with no clutch with out bogging, (stock tall gearing and a 200 lb body). It is not the most powerful low end power I ever had from a 250 2-stroke, (that would be the 97 KX250), but it is not explosive either. I think it is the best power curve i ever had now. Very fun to ride, (I lowered the bike too, a total of 1.75". 1" seat, .75" suspension). PS. I can't stand the modern Batman plastic, so I put on a 2014 front fender, (yes, had to mill new holes, and had to go after market because OEM, 2 of them, were badly twisted. Terrible quality from Yamaha for their old plastic), cut off the silly arrow heads and points, and mounted a 175 gram Frisbee to the forks instead of Thor's arm shield stock number plate, with CNC machined mounting points that I designed and made. Quick release with no tools, in case somebody needs Frisbee when trail riding. It made me laugh when I set the Frisbee on the forks (I was looking for a 1979 ish front number plate), so I mounted it. :) That took more hours than the engine and suspension, probably together. I did a lot of work on that bike to make it a great bike. Bike height, engine, suspension, plastic, custom modified full wrap hand guards, (better than anything on the market), --but it is worth it. So much easier to ride, especially in the woods. Doug in Michigan

[@wjb111]

2 stroke! 💨💨💨

[@scottrugenstein7034]

I cringed when you took the hammer to the front axle threads, never do that again, you will bugger the threads. Try a block of wood, rubber hammer and or a axle pull from the opposite side

[@gohobby9934]

I typically use a rubber mallet.

[@toady..9833]

head squish mod is the cheapest/best mod to do on these 250's motor sounds nice 😎

[@toady..9833]

@user-fz8fy4zl1c gap between piston and the outer part of the head (flatish ring) not the combustion dome, ideal gap is about 1.2mm/1.4mm, mine was just shy of 2mm so alot of air/fuel mix hangs about in there instead of being pushed into the dome part to be ignited

[@EarthSurferUSA]

@@toady..9833 Better yet, if you are using a lower rpm tuned pipe, (FMF Gnarley, Pro Circuit Platinum2 for examples.), if you lower your cylinder with your stock head by not using the cylinder base gasket (seal the cylinder to the cases), you will have about .049" squish, the higher compression, (need 100 octane), and the lower exhaust port will match the lower tuned pipe better. I can't ride it until the spring now, (just built it), but I expect the low end and mid range to be much stronger (kinda hoping for power like my 97 KX250 had), and will probably lose 500-1000 top rpm. But that is fine for my whooped out sandy trail riding. I think 2011-10 and earlier YZ's had a bit higher compression head than the later, by .0085" off the gasket surface. So it would be real close to 1.2mm squish clearance, and may need more a few more points of octane with the lowered cylinder. Mine was just shy of 2mm also stock. .076" I also made the mistake of running 90 octane REC fuel in the stock engine, and got a tinge of detonation damage. The damage was at the edge of the piston/head/cylinder mating surface, on the intake side. That was probably because the stock reed stop plate blocks off about 50% of that rear transfer port tunnel, and some hot ex. gasses lingered there more.

[@EarthSurferUSA]

It worked out great. Very nice lower end power, and not much loss on top that i can tell. I failed to pout a tach on it when it was stock. The power output now makes it much easier to loft the front end at lower rpm's, and is much more fun to ride IMO. Using the FMF Gnarley pipe and v-force reeds with no aluminum spacer plate. Transformed the engine nicely for me. I am sure you will lime ti also.

[@evanstreets8830]

Nice bike mate looks good , love that side stand

[@craigsteinman9807]

they came with chrome wheel..i have a 2016 x model in 17 they were black..yukk..18 they switched to blue..love the blue I am jealous..yzs are great for all skill levels

[@gohobby9934]

2016's had black rims...at least here in the states. Could be different overseas. www.dirtrider.com/2016-yamaha-yz250-five-reasons-this-should-be-your-next-bike/

[@EarthSurferUSA]

Not chromed. Just the color of the aluminum with maybe a clear coat on them. Maybe Hodoka had chromed rims. Not sure. :)

[@EarthSurferUSA]

Let me give you a great tip for putting the front wheel on the forks. For the best fork action and less wear and tear, the fork legs should be parallel, but they won't be with any method I have seen on YT or magazines. I know that because I made a very simple tool (after measurements of a new triple clamp. Cent to cent of the fork legs.) to check it, and the bad methods are up to .5mm off or more. So I found the center distance between the 2 forks, and subtracted the diameter of one chrome lower slider tube. This game be a distance of 5.661" between the 2 chrome lower sliders. (I have the 2019 YZ250. I don't know if that distance is different for other years, but I bet it shares a lot of the years.). The tool: I faced off on both ends, to 5.661" long, a piece of aluminum 1" diameter bar stock, (fits through my brake disk). So I get the axle tight, (I like your spinning method, looking for drag as you spin the wheel.), and the clamp on the disk side tight. Then get that bar stock straight between the lower sliders as low as you can go on the sliders, (through the disk), and tap over the otehr fork leg with a mallet until it is tight, and tighten the last axle clamp Carefully pull it out, (grease the ends a bit if you want). Your forks are now parallel within +/- .001". After I made that tool and set my fork spread,---I had to go to stiffer fork springs as the action now has a lot less friction as it goes through the stroke.

[@EarthSurferUSA]

Factories don't put kick stands on MX bikes because of the risk of you or other racers getting hurt/stabbed by it in a crash. But if we crash in the woods, it does not matter. :)

[@EarthSurferUSA]

That MX14 rear scoop tire you took off,--fantastic for anything golf course hard or softer.

[@user-vb4rj9vv6t]

And no grease on the axles before re-installing???

[@Frostbyte911]

Ive got the same pipe silencer setup on my 99 yz250 I use for single track, I like the combo, didn’t see much difference from the stock pipe in terms of performance, but the bike has plenty of power so I didn’t mind. With that pipe, it’ll rust like an sob, I mean, this video is 9 months old, you probably know, but after a wash, spray some wd40 on a rag and give it a quick wipe down

[@EarthSurferUSA]

WD-40 and a Scotch Bright pad is great looking for raw pipes.

[@kellybrown6988]

Shaving seat is good for enduro

[@frankbirger8278]

Long silencer why not shorty

[@gohobby9934]

It's spark arrested to make it trail legal where I ride.

[@EarthSurferUSA]

@@gohobby9934 I just shortened my FMF turbine core 2 silencer by about 3.625 inches. Moved the spark arrester back just enough to cut off the old body holes. Shined it up a bit, put on new FMF stickers. Looks awesome. I don't pack them tight with fiberglass so they work better (but blow out faster), and I am not totally sure it will pass a DNR sound test, (but I am good with the spark arrester), but I am betting it will. There is actually a electronic switch by your shifter/shift drum. What that does is, when the bike is in neutral, the ignition time is retarded a bit to take the bark out of the exhaust tone.

[@thecitiots]

I took love the sound of the smokers 👍

[@EarthSurferUSA]

They are not "smokers" if they are jetted well. If it has a carb, they are sold rich. The YZ250? Very very rich. It not only smokes a lot, but expels oil droplets from the silencer that ruins the backs of your jerseys. All that oil should be burning, and smoke a bit on start up.

[@thecitiots]

@@EarthSurferUSA I love the name 🤣