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Will I need a spring comressor for a XR100 valve job?

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Will I need to use a spring compressor to change out a bent valve on a XR100?

Is there a specific kind I will need? Any recommendations?

How hard of a job is this?

Thanks!

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yes but a little one will work. There is a problem with valve spring compressors and little Hondas: they are designed for engine with the valve stems/keepers standing above the head casting. The little Honda head castings come up around the stem/keepers blocking the valve spring compressor. My fix is a copper pipe connector with a window cut in the side. Here are two that I built, a simple one on the rigth and one with a collar to fit over the valve spring to keep it from sliding off the spring. It is made from parts of two connectors and a washer, soldered together. The yellow paint is so I can find the critters amongst engine parts and tools.

DSCF1058.jpg

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I did xr80 and xr100's without a spring compressor, but it's not easy. On one, I used a set of vice grip tongs. I think on the other I pressed on the top of the spring with the handle of a hammer. I just did an XR200. I didn't have the vicegrip tongs and the hammer trick didn't work, so I welded something similar to the above photos to a large "C" clamp. This method is much easier.

But the short answer, is that if you pull the engine apart, you will most likely be able to figure out a way to compress the springs, but it won't be easy.

- Brad

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It looks like it even has attachments like the yellow tube cut outs you fabricated your self...

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Yup, that would work fine. It's a nice version of the C-clamp diy one that I made.

- Brad

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So I have some questions on what I have found about my current situation.

Before I tore down the bike, it seemed like the piston was hitting a valve. You could roll it forward in gear, or push down on the kick start for a little bit of travel until it would lock up. You could then roll it backwards and it would free up, and then start it all over again.

I figured that there was a bent valve, so I removed the head. What I found however is the valves were both closed and were definitely not inhibiting the compression stroke. The cam shaft looks fine, everything else seems to be o.k. So what is the deal?

Anyone have this problem? Is the valve bent inside of the valve guide? What should I replace or test?

Let me know what you think!

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If a valve were bent, it wouldn't seat correctly. It sounds like your problem is in the bottom end. To verify this, take the two screws out of the timing chain sprocket and try turning the bottom end without the cam turning. Make sure the valves aren't open while you this.

You will need to hold the cam chain up with your fingers or else it will bind in the lower sprocket and act just like you are describing as your problem.

- Brad

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No I didn't 👍

I'm going into the garage to tinker on it a bit. I'll let you guys know what I find.

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You were right!

I re timed the engine and it could make full revolutions, (valves opened and closed fine) however I did find the TRUE problem. First the cam gears teeth are rounded over pretty bad and second, the cam chain is to loose. Every few revolutions the chain will skip and eventual be way off. I can't get the belt adjustment to make the chain tight, does this make sense or did I mess something up?

Any ideas on what I can do?

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Do I have to split the case to put on a new chain? Of can I feed it down through?

Is the stretching of the cam chain common? Or can My tentioner be messed up?

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You have to remove the stator backing plate and fish it up. It's not too common, but does happen. Also your tensioner could have broke.

Edited by socalxr

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How can I tell if my tentioner broke? How much slack should it take out? I seem to remember when I first pulled the cam, the chain was very tight. The cam gears teeth are very rounded so I think the chain slipped due to that.

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Are there 2 adjustments for the tensioner? I see one on the cylinder head that tightens up the plastic lobe with a half turn, and loosens with a half turn. And then I see an adjustment on the piston cylinder (45 degrees away on the side of the engine facing the front tire) is that also an adjustment? It looks like it could go in a bit...

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Yes, the lower adjustment should be spring loaded. When you loosen the lock nut and then back out the screw, the spring should properly tension the chain. You then tighten the screw and lock nut. You then make fine adjustments using the top cam while the engine is running.

- Brad

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