cliff
Junior Member
Posts: 42
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Post by cliff on Oct 7, 2008 5:54:19 GMT -5
I submit to the forum of smart people this question of my dilemma.
My iginition timing advances to 90 degrees instead of the recommended.
My stator was rebuilt by RMStator out of Canada.
I have purchased a Hyperpak but the advance is the same whether using the stock CDI or the Hyperpak.
Ohm measurements on the stator are all good except the two largerr coils measure about 38% high as opposed to the limit of 30% (Brown and Black 460 ohms and Red Black 465 ohms)
The pulser coil pickups airgap measurements are within specifications.
What do you think the problem might be?
Thanks,
Cliff
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Post by davedunsboro on Oct 7, 2008 7:11:12 GMT -5
Hmm that may be your problem right there ! The fact that the coils read 38% higher in their resistance/more turns, could affect your advance(I actually know for a fact if there are less turns/lower resistance, the bike will not rev over say about 3-4k rpm) The magnetic field will tend to be increased by having more turns ! A little Japanese guru did all this homework 30 years ago & a usually accepted tolerence would be 3-5%+- & I'm sure the normal resistance of the higher coil is 330 ohms . I would firstly make sure that my multimeter is telling the truth & then I would measure a good stator to prove & compare! I've done my share of winding over the years & I know of a few mistakes that I've made(too many turns,too less turns,wrong size wire,connected wrong to name a few)These aren't fun to wind up hence why they are expensive to do! I don't know if I've helped ? Cheers Dave.
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cliff
Junior Member
Posts: 42
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Post by cliff on Oct 7, 2008 8:32:19 GMT -5
Hi Dave,
Thanks for your reply. The tolerances prescribed are actually +-30% for the ohms measurement on the stator.
Cliff
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Post by davedunsboro on Oct 8, 2008 4:12:57 GMT -5
Cliff ,I saw that in the books about the +-30% ,but to me that is a lot of tolerance compared to most electrical things that we deal with in general!I have wound one of these stators allowing for 30% less (250ohms)coz I was being lazy & ran out of room & it didn't work ,the bike would start but was unrideable as it wouldn't go past 3000rpm .So I rewound it to measure 330ohms & it ran perfect ! So I always thought that maybe it was a translation mistake in the books & maybe it should have been +-3% as I was well in the tolerance the first time(its just my theory )I don't know if anyone else has done any work with these & the only way to proove it is to put in a known good stator to try it !(it may not be possible for you to do this).Advancing to 90deg is too much (the books say 26deg I think) .The fact that you've tried the CDI & it didn't change anything rules that out(at idle is it around 5-10deg?)cheers Dave
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cliff
Junior Member
Posts: 42
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Post by cliff on Oct 8, 2008 6:52:04 GMT -5
Hi Dave,
Thanks for the reply and sharing your stator underwind experience and the fact that it would not rev.
There are a few here that understand the interrelationship between the CDI, stator and flywheel far better than I do. Rather than go down another blind alley, ie. new CDI, carb jets etc, I would like to understand if in fact the overwound stator might be the problem.
Someone else alluded to it being the horseshoe coil in the center, which is slightly adjustable around the clock, and that it has a sensor or rather interacts with the magnets in the flywheel.
I overheated the piston and rings in this bike on a 250 mile ride and have since rebuilt the stator. I am thinking this timing advance problem may have done that. At the time I had two bikes and may have mixed the stator flywheel, of course not keeping track from which engine I took parts from. One bike is a '78 and the other an '81.
The bike runs with the 90 degree advance but of course it is rough and does not rev easily. It will go 80 in this config and maybe faster but it does not feel right, as expected. I have another stator but it is in need of a re-wind also. I could send this back to RMStator as there is a one yr warranty but I dont know if the overwind is the problem.
Thanks
Cliff
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Post by davedunsboro on Oct 8, 2008 7:44:04 GMT -5
Thats OK mate ,just putting in my 5cents worth!It's certainly an interesting fault(I'm sure we haven't had this one before & it would be good to be kept in the loop of the outcome for sure.Now there is a bit more history to it as well & I'm sure that you have to match both flywheel & stators(pretty sure this is a prooven theory) so have a look at some older threads on this subject as I think the magnets setup is different ,cheers Dave.
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cliff
Junior Member
Posts: 42
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Post by cliff on Oct 8, 2008 22:28:37 GMT -5
Your 5 cents are very appreciated. I am determined to sort this out no matter what it costs..ha,ha..
I have heard flywheel and stators should match but I don't know why. I have searched this forum and havent found anything. I see forum member sjef says there have been three different stators and flywheel combinations. He says the pickup coil and magnets are in different positions on stators and flywheels. I guess he is speaking of the pulser coil on the stator and magnet on the outside of the flywheel.
There is a '78 flywheel on Ebay now. I may spring for that.
Seems the pulser coil flips a switch at 1950 rpms and the timing advances suddenly from 7 degrees to 26 degrees and then slightly beyond that as rpms increase to 6,000 rpms then it stops advancing. Mine jumps from 7 degrees to the 90 or so degrees and then continues advancing. It is the jump from 7 to 90 degrees that mine is doing with the stock CDI and the new Hyperpak.
Both Pulser coil readings are within spec the charging coils are out being 40% high.
Thanks,
CLiff
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