火箭三R中气缸压缩为零。有人知道原因吗？

wjb said:

Wouldn't there be a de-compressor on all three cylinders?

Click to expand...

I don't know, I haven't opened it yet.

wjb said:

Wouldn't there be a de-compressor on all three cylinders?

Click to expand...

Yes, there is one for each cylinder affecting one of the two exhaust valves.

The "springy" looking things are the decompressors- these are not found on the 2.3 bikes, just the 2.5s. At enough RPM the inertia causes the decompressors to swing out of the way and remain open. When at rest, with the engine in position where one of those valves would normally be closed, the decompressors push down on the bucket (see circled in photo.

JAPANユーザー said:

From the photo, you can see that the left exhaust valve on the exhaust side is leaking, but the right one is not.

Click to expand...

Only one of the two valves is opened by the decompressor.

JAPANユーザー said:

I have checked the spark plugs and there is no problem. I even swapped the spark plugs of the three cylinders and the middle cylinder still did not work.

Click to expand...

As I said- one possible theory. Not the plugs, but possibly no fire going to the plugs. It could also be any number of other things....

To check this put any good plug into the wire and turn over the bike while holding the plug next to the engine. In low light you'll see a spark on cylinders 1 & 3. How about 2?
Also, several of us have found that the plug wires are just resting on the plugs, not seated onto to them (from the factory). Mine ran like this, but I firmly attached them when doing my 10K mile service. It seems possible that if this was the case with yours that the plugs in #2 weren't firing because of that.

Lots of simpler explanations for the issue you are experiencing that, if I were you, I'd be exploring

I have to agree with @Journeyman , it just doesn't seem reasonable to have zero compression in the middle cylinder on a fairly new bike with no visible scoring or anything showing up on a bore scope. . Much more likely to be flawed testing due to the decompressor. Or some other leak

JAPANユーザー said:

Thank you. Next, I'll open the cover and check the reducer. Can you tell me the valve clearance data?

Click to expand...

Yes, go to "Resources" at the top of this page to find where to download the service manual.

I seem to remember that you're nearly at 20K so, if you feel confident in doing this yourself you should find this helpful....

Edit for emphasis (9-26-25)...... Now, when you measure the valve clearances you'll find three of the exhaust valves are waaaay off (much too large). You'll have to swing the decompressors around to get the actual clearance. Ask me how I know....

But....... I still don't know the answer to many questions I've asked previously that I thought might help us help you and, since I've repeated some of them a couple of time, I'm not going to restate them again here. You don't have to answer them.

If you had posted that your bike runs, but has trouble idling, doesn't sound right, kills when opening the throttle I don't think anyone here would have suggested that you first remove the tank, the exhaust, pull the plugs and perform a compression or leak down test. You've assumed a worst case scenario and I don't think I can convince you otherwise, so I think I'll just watch this from afar for a while.

Occam's razor (also spelled Ockham's razor or Ocham's razor; Latin: novacula Occami) is the problem-solving principle that recommends searching for explanations constructed with the smallest possible set of elements. ...... Popularly, the principle is sometimes paraphrased as "of two competing theories, the simpler explanation of an entity is to be preferred." Occam's razor - Wikipedia

Journeyman said:

See my earlier comment about decompressors. They always hold the exhaust valves open until started.

You’ve been committed to a compression problem from the start of this thread. I think the solution is going to be something else much much simpler, but we still need some basic questions answered (see above).

Click to expand...

what ever you do don't worry abut the decompression system. lol
he said "However, when I open the throttle, it stalls."
to me this means it has a big vacuum leak in the hoses or a bad map.
what i have seen on burnt valve or a worn down cam lobe that it works bad at idle then when when revving it does not fall flat on its face. mostly just reduced power.

stingray said:

If you actually have zero compression it isn't going to do a leak-down test. Something is broken.
Do you hear a leaking head gasket?

Click to expand...

Actually, you can

Journeyman said:

As I said- one possible theory. Not the plugs, but possibly no fire going to the plugs. It could also be any number of other things....

To check this put any good plug into the wire and turn over the bike while holding the plug next to the engine. In low light you'll see a spark on cylinders 1 & 3. How about 2?
Also, several of us have found that the plug wires are just resting on the plugs, not seated onto to them (from the factory). Mine ran like this, but I firmly attached them when doing my 10K mile service. It seems possible that if this was the case with yours that the plugs in #2 weren't firing because of that.

Lots of simpler explanations for the issue you are experiencing that, if I were you, I'd be exploring

Click to expand...

There is no problem with the spark plugs, each one sparks.

I spent a lot of effort removing the outer casing today. I wish my fingers were as thin as chopsticks; the space is **** tight. I measured the valve clearance on the leaky side and it's 0.58. The pressure reducing valve moves freely without any sticking. https://youtube.com/shorts/jn3cxFeRvVc?si=y5Tw5lzBl88Lafkx