My '86 project after a LONG vacay from 250R's!

[Jimbo45]

This thread was posted on another forum, but thought I would share here as well!  No need to answer any questions through post #21, since it was just a copy and paste up until then. :sentimental:

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Hey guys! A little backround, I had a ragged out '87 250R when I was 18, back in 1995. I had grown up on 3 wheelers, and always lusted over my friends' 250R's (the '88 version especially), as a younger rider. I traded a junky Mustang for that old '87, and loved every minute. It was white and blue. My best bud also bought an '86, that was red and white, and we raced those things all over the countryside! Good times. I went into the service, and my 250R was sold while I was gone. :02.47-tranquillity:

As I aged, I got into dirtbikes and had a CRF450R and then a CRF250R, and a LTZ400 in there somewhere. Having kids, and no time to ride, and no need for broken bones, I traded my last remaining bike, the CRF250R, in on a Polaris RZR, to hunt with. I figured a 250R was a thing of the past, and I would never see one again. Man, how I recall, and miss that 2 stroke zing and smell.

Well, as luck would have it, last week, a buddy mentioned he wanted to get rid of a quad that needed work. It was a 250R! We negotiated a trade, and he showed up with an awesome example of an '86 250R!!!!!!!!!!!!!!!!!!!!!

8 years ago, the engine was torn down and rebuilt, and that frame powder coated, and new plastics installed. He rode it a few years, and an airbox issue grounded it for the time being, and he got busy with life, and never got around to fixing it. It sat for several years, until now.

It doesn't run yet, but I just acquired a nice OEM airbox and an airbox ring today, and will get the airfilter tomorrow. I know that I will likely need to replace both brake master cylinders, and some other parts, and the rear sprocket seems to have some play on the axle. Will probably do a topend too. I wished he had done the gussets before powder coating, but I don't see any cracks yet, so fingers crossed. First off, I need to remove the carb, a Mikuni TMX (I think its a 36 or 38, haven't measured yet), and clean it out, and inspect the top end while the carb is off. Then, put on the new airbox, and see how it runs! I can't wait!!!!!!!!!!!!!!!!!!! I really wish it had the red '88 plastics, those are my favorite! I may look into doing that, and installing the front and rear lights again. I always wanted a stock looking '88!

Anyway, that is my intro, and I will post updates as I go. Here are some pics from the day I brought it home.

[Jimbo45]

^^^^^  That's how I got it a couple months ago.  Buddy said it sat for a few years, after he quit riding it due to an airbox issue. He had done a lot of work to it when he got it.  He sent me a bunch of pics of it down to the frame before powder, and with the engine split.

[Jimbo45]

Then progress slowed a few weeks, while I got this for $600 ( had to do a little work to it though) for my boy, for Christmas!!!!!!!!!!!!!!!!

[Jimbo45]

Tonight, I had a few hours to work on the 250R. I installed the new airbox and filter and checked out the carb, and it looked reasonably clean in the bore, but there was nasty smelling black gas in the bowl. After a super asinine gas leak from where the fuel strainer bolts to the bottom of the tank (and dumping a bunch of fuel on my garage floor), I got that fixed by adding an additional oring I happened to have, I noticed the gas shut off valve also leaks bad, when in the run and res positions. Dang. But, after hooking everything up, and putting fresh oil in it, I filled the carb bowl, then shut off the valve to prevent another huge puddle. After about a dozen kicks SHE CAME TO LIFE!!!!!!!!!!!!!!!!!!! It ran like crap and was hard to keep going, but it RAN! Since it was 11PM, I decided not to try again, and let it die after about 30 seconds. IT LIVES!!!!!!

So, I have determined I need to fix the gas shut off valve...can you rebuild those? Where do I find a kit? Also, I will need to rebuild the carb, since I noticed all the gunk coming out of the bowl when I drained it. It is a Mikuni TMX 36mm. Where do I find a kit? Where do I find a jetting guide, to get me close, for a starting point, with my setup?

This is so exciting, I can't wait to get it ironed out, and RIDE IT!

Well crap. I spent all afternoon removing the carb and disassembling it, and cleaning it out the best I could. After putting it back together, it ran a few times, briefly, but would climb in RPM, and then sputter out. After a few times like this, it got to where it wouldn't start. I considered rebuilding the carb, but I am thinking I just need to buy a new carb, that might work better. Strangely, I searched for a Mikuni TMX 36mm, and several pop up and are available, but look nothing like mine!? Mine is marked "TMX" on the slide housing, and I measured it at 36.01mm. What the heck? The ones I see online, have a screw on panel, on one side of the slide housing, and generally look different. Mine has no screws on the slide housing. Can someone recommend a low cost reliable new carb that I can purchase, that will work with my stock airbox boot? I am not too concerned with ultra high power, just something that will run clean with my setup. Stock stroke, mild porting, Curtis Sparks MX pipe, uni airfilter in stock airbox, with an Outerwears cover on the airbox. I can't dump a lot of money on this bike, but I need it to run!!!!!!!! Off to the carb/jetting forum............

[Jimbo45]

This is exactly like my carb.....

[Jimbo45]

No pics to add, but I have made some progress. Some of you may have seen my carb post in the fuel/air section. Long story short, I ended up ordering a new Kiehin PWK 38 A/S along with a cable this morning, to start with a better carb. Besides, I wanted to treat myself to an early Christmas present. I was sure that old TMX carb was beyond repair!

So, coming home from work, as I walked through the garage and near the R, I recalled a large nut on the floor from last night. Looking it over, and looking at all the suspension pieces, they were all GTG, so where did it go? Then I saw it.....one of the cylinder base nuts was missing. DOH!!!!!!!! I looked at the other three, and they were coming loose too. There was a good 1/16" gap at the base of the cyl, but the gasket looked ok. Oh wow, am I stupid. I had checked over all of the suspension fasteners, as the previous owner suggested, and the head nuts, but never thought to check the base nuts. Dang. THERE WAS MY AIR LEAK!

So, after supper, I went out, and torqued the cylinder down to 34 ft pounds, and checked every fastener on the engine. Three kicks on choke and the beast came to life, and after a few seconds I turned off the choke and she purred like a kitten. Face palm. YAY!!!!!!!!!!!!! IT WORKS!!!!!!!!!!

The bad news, I have a badass carb on the way that I really didn't need. LOL! Just like the gas shut off valve that dumped gas everywhere no matter how I turned it, and now that I ordered a rebuild kit for that, it hasn't dripped a drop. LOL! I need to name this 250R....something ornery.......

No, its really ok, I am sure the PWK will be a much better carb, and easier to dial in just right.

So, whats a nice, used, clean, Honda CR125 OEM style Mikuni TMX36 worth? :05.18-flustered:

Now, when I get a few hours to add brake fluid and attempt to bleed brakes, and continue checking all the fasteners. grease the rear linkage, and change the oil once more after some running time, I may be ready to ride this thing a bit with my boy, and do some fine tuning, when he gets his 250ex for Christmas! Oh and then install my new carb! LOL

PS......please tell me these things are a bit tappy and knocky at idle. Remember, it has been 18 years since I had one of these 2 strokes. If I recall correctly, my one way back then sounded the same at idle. But, having 4 strokes the past 18 years, I am used to quiet idling. Here is an idle and low rev I took briefly (it was late and I am urban)

[video=youtube;U1BNjKI7F2Q]http://youtu.be/U1BNjKI7F2Q[/video]

Here's another with a rev or two

[video=youtube;WRLkjhlPmuY]http://youtu.be/WRLkjhlPmuY[/video]

[Jimbo45]

A little update. No pics right now, but may get some later today. Got to spend some time on the R yesterday. Went over every bolt on the thing, filled and bled the front brakes (they seem to work) and tried that on the rear, but the master cylinder leaks bad (off to find a nice one, maybe a 450R one). Removed the number graphics, mounted up all the fender hangers, replaced a bunch of fasteners, put a chain on it, etc. Fired right up, and let it warm up. Rode it gently for a few minutes. When stopping I noticed the knocking tapping seemed louder. Made another idle knock video. So, it looks like I am going to take the top end off and see what I find. I would assume I can check for play in the crank and lower rod bearing, after taking the cylinder off, right? Off to find my service manual.......

[Jimbo45]

Plastics off.....



Taking stuff apart............





Engine mount and coolant hoses off.....



Carb and pipe off.....



Head is off...... looks like a small squish area, is this a normal '86 head?



Some scoring in the cylinder, and apparently a domed piston. It was OK to run 93 octane in this?



Jug off, and from my chainsaw repair experience, I know that these marks on the piston are not desirable......

[Jimbo45]

Crankcase looks pretty clean. The con rod feels pretty good. I detected only a very slight amount of up and down movement in the con rod bearing. Just enough to notice, I think it is good for a while, at least I hope so. I didn't notice any crank bearing slack. The wrist pin bearing felt a little loose, but that was without the pin in it, so maybe normal.



Jug bottom....



Cylinder and head......





All ready to roll back into the corner, lower cases covered, waiting for a top end......



Now, to determine the size of the piston, and decide where to get the work done.......

[Jimbo45]

"Here's yer problem!" See video below. The piston had probably more than 1mm of movement in the bore. Guess that was the loud knocking that I heard. I wish I had someone local, that could mic the bore, so I could know what size piston to order. I know that the piston is a 68mm. It still measured 68mm at the center of the skirt, but I suspect the upper and lower diameters were worn down to less than 68mm, causing the play. So what size piston do you guys think I could go with and bore to?

[video=youtube;gPRGFL7rYvM]http://youtu.be/gPRGFL7rYvM[/video]

[Jimbo45]

Hmmm, looking at Pro-x pistons, 68mm is the biggest they sell. I wonder if I could get away with just a hone job and a new 68mm piston? Or, bore it, and get a 68.5mm or 69mm Wiesco piston. Man, I really need someone to mic this cylinder, so I can know which direction I can go.......

Another question for you guys.....this R has a Nology coil and plug wire, that is super long, and you can see the huge loop it makes on the stator side of the engine. What the heck? There probably isn't a good way to sorten this, since it has the ground wire on it, that hooks to the head. Must it be that long?

Picked up a re-sleeved oem top end with 69mm piston, with some life left in it, from 250Ryan today! Thanks bro! Now if my wrist pin bearing arrives before the weekend, I may have this project moving!

[Jimbo45]

New PWK 38 Airstriker! Woo Hoo!

[Jimbo45]

450R rear master cylinder obtained......

[Jimbo45]

Swapped the reservoir and tube and inlet, drilled the threaded mount holes out, and swapped the 250R actuator rod in, and the 450R master cyl is mounted up! Time to head out and bleed it, and see if it works!

[Jimbo45]

Got the gasket set in today and the dowell pins. I didn't realize the engine only used 2 dowell pins on the left side. Doh! I figured each of the four studs needed a dowell pin on the cylinder studs. I wondered why it wouldn't slide all the way down. LOL

I got the top end assembled, and the pipe reconnected, and the new Keihin PWK 38 AS card mounted, but try as I might, even with boiling water, I could NOT get the stock airbox boot on the carb. I heated and stretched, but it was a no go. My boot is kind of ratty, and I was afraid it would split if I pulled any harder on it to stretch it. I guess I will look for an nice stock boot, and boil the crap out of it, and use someting like a shoe stretcher, and make the boot bigger. Man, so many set backs, I WANT TO RIDE THIS BEAST! Here is a pic I took with the new / used top end on.....

Ordered a better used OEM airbox boot (mine was ratty around the carb end) and a reed spacer, to hopefully get this new carb mounted up correctly. To be continued.......