250-500cc 2012 WR360 Project

re: the position you will be at the end of the 2nd swap; that is, to use the 360 in '92 chassis for 1-hour race and the 300 as your main (normal, regular) race bike is sound for this reason alone: the 360 will drain your energy more than the 300 at longer-duration events.

My 360 was the most fun bike I ever had (buddy said my best bike ever), but there was a (fatigue) price to be paid due to having big power instantly on tap at all times. I would never recommend a big engine for a long race. Short one, yes, but not one where endurance is key. If you want to show a thing or three to 450s about acceleration, handling, etc., then the 360 is a fine choice. Just don't expect to do so for hours on end.

Yep, exactly what I was thinking. I just took a bunch of measurements with a caliper. The small bushing has an OD of 18 mm, the new one 22mm. The bolt itself is 17mm, so the thin bushing would be much too thin. This is going to probably delay progress a couple days. I've got some damaged case halves in my parts bin, so I might try to see how it would work out attempting to drill it myself, using a 7/8" drill bit versus a 22mm (availability).

In the mean time, I pulled off the intake and had a look after finally finding pictures of the intake mod. There's not much material there, but I'll see about cleaning some of it up tomorrow, if the drill tests are unsuccessful. My main priority is to get it all together in the frame and fire it up, so I'm not looking to get too crazy on other things yet.

We'll see how it goes, it did take a while to figure it all out when I moved up to the 300 from riding 200s for a decade. For the little bit I did ride the 360 prior to pulling it apart, and I don't think I'll have any problem running it for an enduro. But we will see how I do October 20th at the national.

ohh thats not good, will the 360 swing arm fit your 300? could you use the 360 swing arm and bolt but with washers under the bolt heads?

the problem with that would be the bolts could move around in the frame holes

I can understand why you would do this, had forks and rear shock revalved on my 360 and its no were near as smooth as my 2011 bike. You can not beat the handling of a newer bike. What a shame would love to have a 300 2t frame and use the suspension off the te250meo. Dream Dream.Dream.

I checked on some things. At one point I was going to put a KDX 200 engine in a KX 125 frame, I've got a friend who's done a couple of them. Long story short, on those the cases have to be drilled out and a bit of the case actually has to be machined off to fit with the KX swing arm. Long story short, the case can be drilled out relatively easily, or so I'm told. It'd obviously be better to split the cases and to do it on a drill press, but there are a lot of people who have used a hand drill on an assembled engine with great success.

Time to see what drill bits I can source at lunch. I measured it at 0.8675" which is just a few hundredths mm over 22mm. A 7/8" drill bit will put me 7 thousandths over, and would be very easy to find in either a stepped or regular twist configuration. I don't think the 7 thousandths will be any issue. I should be able to get by with some loctite sleeve retainer if needed to handle any slop.

To clarify, I knocked the bushings from the '92 360 case, and from an '02 250 case I had (cheaper for the whole bottom end from ebay than buying a replacement power valve actuator when it walked away). So, what I'll be drilling is the actual case, which is really soft. Not the bushings which are some kind of hardened steel. Then I'll be inserting the bushings from the 250 into the 360.

Knocking the bushings out of the 250 were a mother f'er. With some heat and penetrating oil, the 360 came out pretty easily, the 250 had me working at it a while.

Kelly, how does the stepped swingarm bolt work? Don't you need to have the larger diameter on both ends, to fit the swingarm bearings?

msmith, what is the ID of the smaller bushings? An alternative method might be to use the smaller 360 swingarm bolt and bush it up for the swingarm bearings and the frame...

I've got all the measurements at home, I can post them up here for reference tonight.

I thought running the smaller axle, but I ruled it out because the frame/swingarm part is the most stressed of the assembly. The engine case really is only there as a spacer for the swing arm and to give a 3rd point of securing the engine. So, in my thoughts at least, there's more room for slop if I keep the bolt the larger size to match the swingarm bearings and the frame.

Kelly, I was thinking that your second style might be the easiest to implement. That's "just" two sleeves at the outboard ends of the bolt, each sleeve going through the swingarm bearing and frame. The two styles are not actually much different, it's just a matter of having the sleeves all be separate pieces, or having the first one be part of the bolt. Either style would be easy for someone to manufacture on a mill/lathe.

msmith, the smaller bolt diameter is apparently sufficient for the 360 bikes, so it would probably be acceptable for your bike too, and that solution is fully reversible. If you drill out the case holes, you will need to have custom bushings made in order to reassemble everything back onto the 360 frame when this is all over. That being said, that's actually not a bad solution, as it gives you the big swingarm bolt in the short term and it isn't too hard to whip up a custom set of bushings to put the motor back to "stock" later.

sweet project!

The closest thing I did to something like this was when I swapped an 07 YZ 125 engine into an 08 YZ frame... lol

just use some bushed to stop small swing arm bolt wobbling that fit straight through thr 250 bearing inserts no? so all clamped in position and all reversable all you would need is two large washers and two bushed the width of the swing arm bearings to the outter of frame. does that make sence, i gather your determined to get it done but the quickest less damage way is usually the best.

If you would have had any true friends when you did the Yamazuki they would have done an intervention. Recognizing the problem is the first step to the cure.

I One swapped a 331 caddy 8 into a 49 studebaker

Alright, time to take a step back to explain what I'm doing, and why I'm going this route.

Here is a Microsoft Paint illustration to help show whats going on.



Black = Swing arm bolt
Grey = Frame
Red = Swing arm
Blue = Engine case

The frame at the point the bolt goes through is a single thickness of steel, with a 17mm hole drilled through it to match the swing arm bolt. This size matches the swing arm bearings and the bushings in the original engine case.

Using the method I'm doing, which is enlarging the hole in the cases, then inserting the bushing that matches the larger swing arm bolt, keeps all of the original stressed pieces from stock. The frame and swing arm take the brute of the punishment, so it seems that would be the most important part to leave as is. The drawback to this is the 360 cases will be fit for the larger bushings and the old bushings will not be able to fit back in. This would be handled with 2 new bushings being made that would end up having a thicker spacing than either the old or new bushings, making this probably a fair upgrade for the '92 anyway.

The method that is mentioned using the smaller swing arm bolt, and putting spacers inside the swingarm and frame could work, but for me my concern is that that spacer is going to be pretty thin. I believe the new and old swingarm bolts are only 1 mm difference in diameter, so that would be .5 mm on either side of the bolt. Now add to the fact, that the new spacer needs to be a very tight fit to both the frame and the bearing with an exact length, that cannot deform when torqued down, and issues start coming up. What if that spacer crushes down and only contacts halfway across the frame metal? Overtime during normal use that will elongate the hole and the frame will be scrap. Usually when a dirt bike frame gets "worn out" it gets loose at that swing arm bolt and the handling gets sloppy, I don't want to do anything to have that happen prematurely.

Since the engine case is really only used as a spacer between the legs of the swing arm when the bolt is torqued down, there is really very little risk of long term wear being affected.

I keep hearing or actually in this case reading, sleeves but the difference in size is not that great
so you push a sleeve through the bearings and meet the engine bushings, if there is not a decent mating surface when you torque the swingarm pivot it could get ugly, what if it chaffed a little due to only having a small pressure surface then it starts inside the engine bushings now you have an unrideable bike