JH600 Valve Problem

[MotoKai]

A week ago I was riding in Suzhou and started to hear a rattling noise upon arrival. I've had chain issues with the JH600 before (emailed some of you on the rubber guard issue), as well as general chain slack which has needed tightening. While out in Suzhou, it was tightened up once again but the tapping sound could still be heard on the way back to Shanghai.

Few days later I rode out to local mechanic in Shanghai to have him check the chain. We opened the front sprocket cover and could see the chain "jumping" a bit. Upon further inspection of the chain, it was obvious that as it rotated around the sprockets it went from being taught to loose to taught. Seems there was damage to the chain which created irregularities throughout. A call was made to the local Shanghai Jialing representative to discuss all the issues, and we agreed to swap the chain for a new KISS O-link.

The change was magical. There was more consistent pull through the gears and it moved from 1st thru 5th without effort. [FYI: Mechanic suggested I find a better chain lube which can penetrate the inner-core of the links and keep it properly conditioned.]

Pleased with my new ride I was off to install my new Taobao handguards, but the noise was coming back again, this time more noticeable. Louder now, I could tell it was coming from the front of the bike, and the sound was more clear. A pinging (Shit, my engine! )

After handguard installation, I rode back home with one of the guys from the Jiaoji Lu Motomarket, and it was now loud enough that he could hear it from on his bike sitting next to me at the red light. He suggested it was the timing chain.

Next day I was back at the mechanic, and he checked the timing chain adjuster, but this didn't solve anything. Another call was made to the local Jialing representative, and he suggested to take it to Pudong to see "The Dr." He's The Dr. because he can confidently strip down a bike and reassemble before I can finish looking up translations of the first few parts that come off!

Rode out to Pudong to meet him with euphonius and watched him go into action. After opening up the bike to check, he determined that it wasn't the adjuster or the timing chain itself....but the 减压阀 (jianyafa) - the valve.



Before the replacement could be sent from Chongqing, I was asked to bring the bike back to The Dr. so he can actually open the cylinder head to inspect the valve. This was done with amazing speed (The Dr. cursed Chinese engine design thru the whole process - he normally works on Japanese bikes which have much better design which makes working on them much easier). Well yes, it was as he determined - bad valve (see red circle below indicating area of issue which was loose and creating the rattle).

Enough backstory, on to the photos:

[Lao Jia Hou]

Very interesting.

Do you know which actual part was loose and was therefore tightened/adjusted/replaced? The red circle seems to be highlighting something by the cam/rocker. Hard to tell, but is that a rocker arm to the right of the circle? (the vertical metal piece that appears to disappear near the base of the lower right valve).

I am guessing that the ticking followed the RPM changes? i.e., more ticking as RPMs increased, less ticking as RPMs decreased? Was there the same volume of ticking in any RPM, and was it consistent? (i.e., no missing ticking)

Not sure about the chain thing. If you are watching a chain go over the front sprocket when the bike is on the centre stand, at idle, in gear (with the rear wheel lifted), it might appear that the chain is tightening/slackening ... and you might see some "apparent chain slap" in the main run of the chain (the "slack" area between the two sprockets). This is caused by a load/no-load situation where the chain tightens to spin the rear wheel, but then the wheel speeds up and actually spins faster than what the chain is causing, so the chain momentarily slackens. Then the rear wheel slows a bit and the chain tightens to turn it, again. And so on. When a "slapping" chain (btw, it isn't really slapping) goes over a smaller sprocket, it appears to be occasionally lifting off the teeth.

BTW, a common situation happens when people "adjust" a chain when it is on the centre stand, using the owner manual's specs. The specs (usual free travel of about an inch) are intended for when the bike is resting on the ground with its riding weight (i.e., rider & gear). Obviously, you need two people (one to sit on the bike, one to measure the chain's play), but after you have set it with two people, throw the bike back on its centre stand and measure the chain play in its unloaded state. Depending on the geometry of a bike, a loaded bike causes a chain to be "loosen" because the distance between the sprockets decreases as the suspension compresses.

In my experience, one actually has to feel, by hand, each link to see if they move freely. If you can visually see a frozen link move over a sprocket, I'd have thought you'd hear it first. And I think there is considerable debate about using anything that penetrates an O-ring.

BUT .... if you noticed a big difference with the new chain ... hmmmm. Interesting. Did you inspect the old chain? Were some links indeed frozen?

Anyways, thanks for the info re our lovely JH600s. Fortunately, we haven't been freaked out by anything near the BMW 650GS fork problems that seem to have recurred. Check this out for a scary story ...

BMW front fork failure.

[MotoKai]

Do you know which actual part was loose and was therefore tightened/adjusted/replaced? The red circle seems to be highlighting something by the cam/rocker. Hard to tell, but is that a rocker arm to the right of the circle? (the vertical metal piece that appears to disappear near the base of the lower right valve).

I am guessing that the ticking followed the RPM changes? i.e., more ticking as RPMs increased, less ticking as RPMs decreased? Was there the same volume of ticking in any RPM, and was it consistent? (i.e., no missing ticking)

Thanks for the input LJH.
I don't know the details of the actual part affected, just that it is with the 减压阀 (valve) and specifically the area I highlighted in red. At a certain point it gets lost in translation, so if anyone here has additional info, I'd be very interested to learn more. Something with the cam/rocker?? What usually causes this part to fail?

The ticking wasn't specifically related to the RPMs as even after getting on the throttle I would sometimes hear the sound increase after letting off (when the RPMs were in fact lower). In general we couldn't detect anything consistent between the sound and the RPMs.

In my experience, one actually has to feel, by hand, each link to see if they move freely. If you can visually see a frozen link move over a sprocket, I'd have thought you'd hear it first. And I think there is considerable debate about using anything that penetrates an O-ring.

BUT .... if you noticed a big difference with the new chain ... hmmmm. Interesting. Did you inspect the old chain? Were some links indeed frozen?

Yes. I failed to mention that when turning the chain by hand around the sprockets, there was a squeak in the rear sprocket at one specific point. After replacing the chain, the old one was inspected and a frozen link discovered.

[Lao Jia Hou]

Hi MK

Upon looking at your pics again, it looks like the rocker arms were removed as an assembly when the top end was removed. Your valves will be under the four springs' caps, showing in the last pic, far away from the red circle. The red circle seems to highlight something on your overhead cam shaft, that is exposed/accessed by that little open tab. I am not sure what that little open space is for, or what is underneath that was the source of your problem. It might be driving something else off the cam's rotation?

I'm not familiar with the internals of the JH600 engine, having never taken mine apart (heaven forbid!), but it looks like the cam has only one node for both the intake & exhaust valves. I looked at that parts manual we all have, but it doesn't give a clear picture, nor a proper explanation. And, of course, it is all in Chinese.

My two-wheeled JH600 purrs without any glitch, but my sidecar JH600B has an occasionally noisy engine, emitting some strange noises. I've wondered about incorrectly adjusted valves on that bike, but then I thought that the JH600 engine didn't require valve adjustment maintenance? Hence, I am very curious as to what the source of your problem was, and how it was remedied. My "B" might be needing the same, or at least it is very helpful to know what you uncovered.

Cheers

[euphonius]

This is definitely an issue of translation, compounded by our relative naivete (Motokai's and mine) about the inner workings of our engines.

I had a long conversation with Dr Cui, trying to understand the function of this 减压阀 (jianyafa), which dictionaries indeed translate as "valve". Cui confused the hell out of me by insisting that the JH600 "has only one valve" -- when I knew perfectly well that it has four valves. I was using the terms 排气 (paiqi exhaust) and 进气 (jinqi intake) but couldn't remember the full term for the respective valves -- 排气门 paiqimen and 进气门 jinqimen. So Dr Cui stood his ground and insisted that there was "only one valve".

So if the thing in the red circle is indeed something referred to in Chinese as a 减压阀 (jianyafa) aka "valve", what function would that valve have and what might it be called by a competent English-speaking motorcycle mechanic?

Oh, and for the record, as Motokai and I rode home that day, with my own senses heightened by Motokai's predicament, I could hear through the lovely exhaust thunder a clattering of engine sounds, the sounds of metal banging on metal, of gears being put to the test. Not the same tapety-tapety that MK's JH was making, but a quiet symphony of its own. She's running beautifully.

cheers

[MotoKai]

Exchanged sms today with nostalgia, as he's arranging a moto event this weekend in Shanghai (Ferarri Festival @ F1).
After telling him I may not be able to attend due to the above matter, he provided some consolation since his JB already went thru some work related to his 减压阀(getting interesting LJH?).

Check out this link to see more of Dr. Cui's work, in particular what he's done on nostalgia's JB600: http://www.mychinamoto.com/forums/sh...ll=1#post18041

Hoping in the next day or two to get a bit better understanding of "what that little open space is for [and]....the source of [my] problem."

[MotoKai]

The little open space: 这个叫凸轮轴减压器,作用是当摩托车起动时,让排气门打开,使起动转速快速达到规定转速,当车发动以后,这 个减压器就不起作用了
The function of the camshaft regulator (凸轮轴减压器) is only to open the exhaust valve when the motocycle starts, so that the motobike can accelerate from its start speed until it reaches a steady fast speed.

[Lao Jia Hou]

The little open space: 这个叫凸轮轴减压器,作用是当摩托车起动时,让排气门打开,使起动转速快速达到规定转速,当车发动以后,这 个减压器就不起作用了
The function of the camshaft regulator (凸轮轴减压器) is only to open the exhaust valve when the motocycle starts, so that the motobike can accelerate from its start speed until it reaches a steady fast speed.

I did a quick Google search on "camshaft regulator" and discovered that it relates to sensing engine timing on EFI engines. I'm old school, and can fuddle my way around old technology, but whenever EFI or ECM stuff comes along ... it's off to the experts.

So, the camshaft regulator probably sends info to the ECM, or EFI, or both, to alter fuel delivery? I can't see how opening a valve (which is a fixed mechanical event) can be modified by the engine ... but, then again, there is something out there called "variable valve timing" (VVT) on certain cars. Who knows how that works? Maybe the cam is multi-piece and can rotate internally, adjusting the camshaft lobes' effect for valve timing?

The magic of an engine always comes down to that combustion chamber, that requires all valves being closed during the compression & firing strokes. But the timing of when intake & exhaust valves open is supposedly controlled by the camshaft spinning around, with its bumps (lobes) lifting one end of a rocker arm so that the other end of the rocker arm pushes down the valve (to open it up to allow fuel/air to come in ... or just air in an EFI engine .... or to allow exhaust gases out). Back in the old old days, there were mechanical thingies that advanced/retarded timing of ignition. I have no idea how it works now.

Re the 600B ... yeah, I saw that depressing post by nostalgia. I've toyed with the idea of swapping out the B's entire engine/tranny/controls for a regular JH600 engine. Jialing says it can't be done, but I've some contacts in the military that say they have done it. One loses the reverse gear, but that is ok.

Thanks very much for sharing your experience. I really feel helpless without an English service manual for these bikes. Bit by bit, though, we can learn from each other.

Cheers

[zhu]

i think what you are looking at there is the decompressor which holds open one of the valves when the engine is spinning on the starter.
it should then allow the valve to operate normally once the engine fires

and yes it will make a hell of a racket if it gets out of line

[euphonius]

i think what you are looking at there is the decompressor which holds open one of the valves when the engine is spinning on the starter.
it should then allow the valve to operate normally once the engine fires

and yes it will make a hell of a racket if it gets out of line

thanks, zhu.

I'm looking at the exploded diagram of the JH600 upper head, with the camshaft and valve assemblies, and can see this part clearly. Alas, I cannot make out in the diagram how it is activated and how it links to the intake/exhaust valves. I've googled a bit for "decompressor single-cylinder four-stroke motorcycle engine" and the like, but not found anything truly instructive.

So what you and Lao Jia Huo seem to be saying is this mechanism intervenes in the normal exhaust/intake valve operations during and only during startup to achieve some desired effect, such as, err, starting up the engine? Or starting it up more efficiently/smoothly than in the absence of this mechanism?

EDIT: Hmmm, I do have contacts for a guy here in Shanghai who's with the liaison office of AVL GmbH, which provided the design and engineering for our JH600 engines. I'll try again to track him down.

Motokai and I did get a glimpse recently of the phone-book sized JH600 shop manual, all in Chinese of course, and damn I'd like to lay my hands on one of those. The guy who is working on Motokai's engine does NOT have one of these shop manuals. There's probably only one in all of Shanghai.

Wonder if Jialing would sell me one, as they did with the service parts catalog?

cheers