XR200R - Need compression lifter measurement.

[TobyS]

I have a weird configuration on my '88 XR200R head. It had a non-stock decompression cam of some sort. I'm talking about the little shaft in the head with the lever welded on it that hooks to the cable that goes down to the kickstarter.

Anyway, I got a replacement lifter, and it is too far off the cam. It rotates 180 degrees before even coming in contact. I know I have it set up right.

What I would like is if someone has a lifter shaft (hopefully out of the bike), can they measure the shaft from the flat to the round of the shaft (i.e. the front to back of a capitol "D". My measurement is .160" or 4mm. You can pull the lifter shaft out by removing the 10 mm bolt on top. It slips in and out easy.

Thanks,
Toby

 

[Jon K.]

I can probably put my hands on one tomorrow (Monday) evening, but in the meantime; back up a little.

Is the lever actually different from the original? Why would this be? Did it come out of a wrong motor or something?

Did this lever work at any point? And quit working? Or did it never work as long as you have had the bike?

Not wanting to pick your question apart, just trying to understand what might be going on.

Working from memory; I believe the exhaust rocker has a flat on it that accomodates the decompression lifter. Could the rockers have been switched somehow? An intake rocker where the exhaust should be? Stranger things have happened.

This is a two-valve head eh?

 

[TobyS]

JonK,
Thanks a lot for the reply. Glad to provide more detail. It's an '88 with a two valve head. I bought it used, and couldn't talk to the actual owner, because he was in poor health. The bike ran well. There was no compression release cable routed to the kick starter area. The guy did have a compression release lever on the bars, that he probably planned to connect for some reason. This is not a stock deal. There were signs that the engine had been torn down (non standard gasket goop, and bolts). Overall, it was in great shape, and pretty cherry.

I installed the decompression cable to the kick starter after I got it. The cable was at the absolute end of its adjustment (loose as possible). Also, the head fins are ground away slightly to allow the arm to rotate further counter clockwise. My wife has ridden the bike infrequently for the last few years with real problems. I was working on another problem (vacuum leak) when I noticed that the decomp lifter arm was welded on by someone with less skill than Honda.

I took out the lifter shaft, and instead of the flat on the "cam" of the shaft, it had an offset shaft on the end about 1/4" diameter. This is in about the right position, and it almost works. It has been for a while. However, it binds, kind of like it is high centered, when it is engaged. This causes some noise when it's running, like it is interfering with the rocker arm. I got a stock decomp lifter thinking it would be an easy fix. The bike runs great, and quiet with the stock lifter in place.

However, the stock lifter doesn't open the valve. It's got about .040-.060" clearance. The lifter is probably right, but I want to rule it out. It's probably the rocker, or maybe an oddball aftermarket cam.

If you have stuff to look at, I'd be interested in what the step on the side of the rocker looks like. Maybe mine's ground down, but it doesn't look like it. I've got the engine together, and I can only see it through the shaft hole. It's got a cast tab on the side of the arm, and that is spotfaced down about .125"

Also, if you can tell me about how much thread sticks out of the valve adjuster nut on the exhaust, that might give me a clue about if it's the cam or rocker.

If it were me, I'd just forget the autodecompression, but my wife can't start the bike without it.

Well, you asked for more detail.

Thanks,
Toby

 

[Jon K.]

Toby; thanks for the extra info. Again, working from memory, there is not much thread sticking out of the adjuster nut. If you have a re-ground cam, there would be even less.

The adjuster will "high-center" if working properly. When it swings around, the ecentric pushes the rocker open, and there it will stay until the cam opens the valve further, allowing the decomp lever to spring back.

If you try to use the bike without a decompression lever, you will eventually break the kickstart gear, and promptly have to split the cases.

I have a motor on my workbench, and will look closely this evening, and report back.


Jonny

 

[TobyS]

Jonny,

These are all good points. My dealer's mechanic said forget about the decompression unit, and disconnect it. I share your concern. It's a pain that the kickstarter is in the center cases.

The weird thing about the dc lifter is that the excess clearance I'm talking about would only be caused by the lifter being too large in the minor diameter, because the lifter is too far away from the decompressor cam.

You're right about the travel of the cable limiting the high center movement, and possibly that the lifter will return because of spring pressure. I might find a way to move the cable anchor to a better place, so it adjusts properly. Right now, it makes noise and runs a little wierd.

Anyway, in a perfect world, I'd trust Honda and put it back together the way it is designed. Hopefully I can figure that out without spending too much money.

Thanks,
Toby

 

[Jon K.]

Oops; by the time I got home last night, I was beat. I didn't get out to the shop like I had hoped.

I will make another run at it this evening.

 

[TobyS]

No worries. The amount of threads showing on the rockers would be nice to know. If I recall, mine had about .060" above the nut. If that's high, it could point to the rocker or cam. The seat isn't ground deep, so that's not it. If I do take off the cam cover, I can measure the minor diameter of the cam. I think that spec is in the book.
Thanks,
Toby

 

[Jon K.]

Toby;

I got out to the shop last night, and have the piece in my hand.

First, the weld does indeed look like an 8th grade remedial class did it.

There are three threads protruding through the locknut. I am pretty sure this is a stock cam.

There is indeed a little "ledge" built onto the rocker to accomodate the decomp mechanism. The intake rocker does not have this ledge.

The decompressor itself is a round shaft with a smaller round shaft protruding 6mm from the end of the main shaft.

The small shaft is a diameter of 6mm. It is offset from center of the larger shaft by 5mm. That is, the center of the small shaft is 5mm off the center of the large shaft.

All of my stuff came out of an '82 model, but I would expect them to be the same.

The pieces up top that actually crack the valve are really pretty simple. The lower mechanism is much more complex. All the gears, decompressor cam, and shaft have to be timed. There are marks on all this stuff, and they are pretty staightforward, but if they get off a tooth (or a spline) or two, the mechanism is pretty much doomed.

Hope some of this helps; please report back on your findings.

Jonny

 

[TobyS]

That's exactly what I needed to know. The dealer said all the lifters have the same part number. Now I'll have him look at an '82. It should have a different number, and I expect the rocker to be different too. Mine's an '88, so someone may have fitted a different lifter and valve to it.
Thanks again,
Toby

 

[TobyS]

I meant different rocker, not valve. Apparently I don't have editing privileges.
-Toby

 

[Jon K.]

Panic mode!!!

The distance from center is 1mm!!! :eek: This gives it a total "travel" of 2mm.

I had if figured wrong!! Darn mathmatics!!!