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ned37
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- Joined
- Dec 13, 2004
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- back in cottonwood, az
when i had my 04 with the dutch clog apart and back together, it seemed fairly tightly wound, and when doing the 02 650 (twice), one spring felt tighter than the other, but they looked identical. neither one needed prompted.
Taff. Have you ever seen a bike where the decomp sometimes fails to actuate at all? (ie occasionally deoes not come back in) It should make itself fairly obvious when you kick it.
Also, at what speed is the flyweight supposed to fly out? I can vaguely remember Dale mentioning it. He put the camshaft in the lathe & wound the speed up till the decomp clonked out. I thought it was of the order of a few hundred camshaft RPM. It sounded like a good way to test it.
Also, at what speed is the flyweight supposed to fly out? I can vaguely remember Dale mentioning it. He put the camshaft in the lathe & wound the speed up till the decomp clonked out. I thought it was of the order of a few hundred camshaft RPM. It sounded like a good way to test it.
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- Nov 20, 2001
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- Ely, England
the thing is...the new decomp spring essentially has it's tail go across the middle of the end of the coils. you would expect to put the lobe into the 'C' part but you can put it outside this. i've seen this trouble before but i can't recall how i cured it.
regards
Taffy
regards
Taffy
ned37
Moderator
- Joined
- Dec 13, 2004
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- 2,462
- Location
- back in cottonwood, az
looking at the side view of a decomp, the earlier decomp and its spring flat sits at the top from 12 to 3 oclock with no groove and is held in place by a double bend. i think the double bend and the lack of a side to side locking groove causes a variability in tension. ( 1st pic )
the dutch clog and its spring flat sits from 3 to 6 oclock in a groove held in place by a single bend (2nd pic).
the dutch clog and its spring flat sits from 3 to 6 oclock in a groove held in place by a single bend (2nd pic).
Attachments
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- Ely, England
i've sorted this today. if anyone will host the photo please PM me your email address.
i have taken the long arm of the spring as it straightens to move away from the coils and i've bent it back to bring the point striaght down onto the flat of the cam. this has the effect of twisting the spring a further 60-90 degrees.
the decomp works a treat now.
regards
Taffy
i have taken the long arm of the spring as it straightens to move away from the coils and i've bent it back to bring the point striaght down onto the flat of the cam. this has the effect of twisting the spring a further 60-90 degrees.
the decomp works a treat now.
regards
Taffy
- Joined
- Feb 19, 2003
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- 3,227
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- Escondido, Ca. USA
Taffy said:
Taff, just upload to your gallery. Then when viewing the enlarged image in your gallery right click on the image and choose properties. Copy the url address and paste it into a post using the image tag then close the tag. Your image will then be inserted into the post.
Or, just use the attachment function per Ned.
- Joined
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- 3,227
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- Escondido, Ca. USA
Odd, I could not upload the photos as an attachment. The error message stated that the picture was over the 1200 x 1200 pixel limit, which its not. I could upload it to my gallery though. How old is your camera? I don't know what it is but I am guessing that there is something the new site format doesn't like about your camera.
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- Nov 20, 2001
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- Ely, England
yet again i've had trouble, even with the above hook. there is considerable friction between the bobweight and the hardened shoulder of the cam.
hopefully, below, eric will plonk a couple more photos to demonstrate this.
when the cam is the wrong way up, the decomp bob hangs below the cam and can't get back to the inside shoulder. so we have no decomp. this means kicking full compression!
on assesment it becomes clear why!
the decomp spring has far too many turns to it. the grooved shoulder for the location of the spring needs to be nearer the exhaust lobe to allow the spring to become free'd up. IT'S COIL BOUND! it's not only coil bound but means that the decomp lobe is forced hard against the shoulder of the cam. because both surfaces are flat but unpolished there is a lot of friction.
my latest answer has been to bend even more spring but this time let it run around the body of the cam.
you'll have difficulty spotting it in the photos but like for a shiny wire!
this gives me more tension but slightly less wire. all i could do on this occasion was to grind the shoulder of the cam slightly so the bobweight has no friction.
in the future i would like the thinnest shim of say .005" (0.1mm) on the base of the decomp shaft to seperate the cam from the weight.
regards
Taffy
hopefully, below, eric will plonk a couple more photos to demonstrate this.
when the cam is the wrong way up, the decomp bob hangs below the cam and can't get back to the inside shoulder. so we have no decomp. this means kicking full compression!
on assesment it becomes clear why!
the decomp spring has far too many turns to it. the grooved shoulder for the location of the spring needs to be nearer the exhaust lobe to allow the spring to become free'd up. IT'S COIL BOUND! it's not only coil bound but means that the decomp lobe is forced hard against the shoulder of the cam. because both surfaces are flat but unpolished there is a lot of friction.
my latest answer has been to bend even more spring but this time let it run around the body of the cam.
you'll have difficulty spotting it in the photos but like for a shiny wire!
this gives me more tension but slightly less wire. all i could do on this occasion was to grind the shoulder of the cam slightly so the bobweight has no friction.
in the future i would like the thinnest shim of say .005" (0.1mm) on the base of the decomp shaft to seperate the cam from the weight.
regards
Taffy
- Joined
- Nov 20, 2001
- Messages
- 17,028
- Location
- Ely, England
thanks eric and adding to what i said previously: you know those african tribeswomen? they have extra long necks and rings round them - well now you know how the decomp feels!!!!
oh and seconds later i spotted the washer on the bench for that far bolt so don't have a go at me.
regards
Taffy
oh and seconds later i spotted the washer on the bench for that far bolt so don't have a go at me.
regards
Taffy
Hey Taff
Was thinking about what you had said here. Had to strip some bits & the rocker cover was only half a dozen more bolts. I hadn't been in the cambox before.
My decomp might as well not have a spring on it at all! Rotating the engine slowly the "flyweight" falls out onto the stop bolt under gravity just after it rotates past the bottom of the cam chainwheel then flops back in when it goes past the top.
I was thinking of pulling the cam and trying to preload the flyweight spring one whole turn. The '98 service manual says stuff-all about how to install the spring. Do you think the spring would be able to do this? Might help the starter work better?
Can't fault anything else in there. It looks original and has the early aluminium sprocket which looks in good order.
Also, can you remember what diameter wire the flyweight springs you have seen are made from and how many turns they have? Mine seems to be 15 turns of 0.50mm wire.
Was thinking about what you had said here. Had to strip some bits & the rocker cover was only half a dozen more bolts. I hadn't been in the cambox before.
My decomp might as well not have a spring on it at all! Rotating the engine slowly the "flyweight" falls out onto the stop bolt under gravity just after it rotates past the bottom of the cam chainwheel then flops back in when it goes past the top.
I was thinking of pulling the cam and trying to preload the flyweight spring one whole turn. The '98 service manual says stuff-all about how to install the spring. Do you think the spring would be able to do this? Might help the starter work better?
Can't fault anything else in there. It looks original and has the early aluminium sprocket which looks in good order.
Also, can you remember what diameter wire the flyweight springs you have seen are made from and how many turns they have? Mine seems to be 15 turns of 0.50mm wire.
- Joined
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- Ely, England
whato mate!
yes you can recoil the whole thing up and get it working again. just make sure that it's tight on the 'D' section.
my spring has 16 coils at the back and 14 at the front.
you'll know to look at the tip[ of the lobe and its condition?
nothing else to say really - thats about it.
regards
Taffy
yes you can recoil the whole thing up and get it working again. just make sure that it's tight on the 'D' section.
my spring has 16 coils at the back and 14 at the front.
you'll know to look at the tip[ of the lobe and its condition?
nothing else to say really - thats about it.
regards
Taffy
Just preloaded the decomp spring one complete turn. It now flicks out at about 550 camshaft RPM & drops back in again at a bit less than 500. Will see how it goes.
Cripes the pre-2001 cams are out of balance when the weight swings out!! Shook crap out of the drill at about 2500 RPM. Looks like the later ones are balanced better with the large holes in the sprocket.
Cripes the pre-2001 cams are out of balance when the weight swings out!! Shook crap out of the drill at about 2500 RPM. Looks like the later ones are balanced better with the large holes in the sprocket.
Got it running yesterday with the pre-loaded doecomp spring. First impression was THE BLOODY DECOMP MUST HAVE NEVER WORKED SINCE I GOT THE BIKE!!! It magically starts easily on the button now.
I guess it does prove it is possible to run the early models without a decomp at all if you use both the estart and kick start together.
I do suspect the decomp spring prewound one whole turn might be a tad too much preload. It idles fine, but when you drag the idle speed down with the clutch you can hear the decomp click in every now & then. It doesn't stop the bike, but I think if it happens too much the decomp will wear prematurely. Chances are the spring will sag some more & this will improve.
I guess it does prove it is possible to run the early models without a decomp at all if you use both the estart and kick start together.
I do suspect the decomp spring prewound one whole turn might be a tad too much preload. It idles fine, but when you drag the idle speed down with the clutch you can hear the decomp click in every now & then. It doesn't stop the bike, but I think if it happens too much the decomp will wear prematurely. Chances are the spring will sag some more & this will improve.
- Joined
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- Ely, England
my latest way of fitting the spring is to unroll it a full turn and a bit until the wire points in the same direction as the other end that bisects across the middle. i then snip 30mm off and fit. by the time i've wound it up now it's just about spot on. and i can always make the inverted 'V' with the tail to make it even stronger if i need too.
regards
Taffy
regards
Taffy
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