Lightening flywheel on the XR650R in progress.


57 replies to this topic
  • crmc33

Posted November 21, 2007 - 04:36 AM

#41

Oh dear - it sounds like they messed up your igintion timing. :thumbsup:
FYI, its well worth continuing with the mod. I have removed my rotor completely from my 650L racer (ie total loss ignition, the pickups on the 650L being on the RHS of the crank) and the engine spins up so quick Ive had to beef up the clutch.
Stick with it, tho you are likely to have a problem with easier wheelies and/or clutch slip using std springs but Id get the rotor as light as you can if you want fast response.

HTH! :ride:

  • BWB63

Posted November 21, 2007 - 06:53 AM

#42

Rich, maybe you can move the ignition sending pickup in some to alline it with more of the meat of what is left of the pulser (what ever you want to call the part that got shaved). I noticed that the sending pickup is not truley allined in the middle of the pulser and maybe there is enough mass left, you just have to alline them to cautch the best mass. Hope that makes sense.

  • Thumpage

Posted November 21, 2007 - 02:28 PM

#43

CRMC, I will still be pursuing this mod no doubt. It looks like I will have to start over again. That gets into the other part of the story...

Bruce,

I had done just what you were saying to see if it would correct the problem and it was a no go. I did this just to see what would happen at the suggestion of Procycle. But I will make a point which I am sure you will understand. I or anybody else should not have to do any other unnessessary modifications, (it didn't work anyway though) like this for such a simple, straight forward mod such as lightening the flywheel. This starts to get into another part of the story which I will refrain from at the moment.
In any case, spacing the stator pickup did not work. It may have seemed to lessen the condition just a wee bit but the same thing occured. Bigtime missing/cutting out and backfiring. I tried 8mm bolt washers under the stator pickup, then went to two washers and it still didn't work. That is all you can really go without effecting the stator pickups alignment in a slight other way.
The clip bracket of the stator pickup has alignment ridges underneath that set into the recesses of the mounting holes on the stator cover. They are long enough to still do their job with one washer sandwiched underneath. (It just so happened that 8mm bolt washers were sized just right, in order to fit over the raised alignment 'rings' of the bracket. But with two stacked washers they become ineffective in keeping true full alignment since the raised edges are no longer than the width of two stacked washers. You can keep it close by eye as you tighten down the bolts but it is just not proper. The bracket also holds the wiring against the stator cover to keep from moving. Once it is spaced out, it would have to be bent to keep the wiring held. I have included pics below to help explain the details up to this point.

As a note; The homemade flywheel holder that we talked about before did not work in being able to hold the flywheel enough to apply 92 Ft Lbs. of torque for installing. It held to about 45-50ft lbs and that was it. I bought a 18V battery operated impact wrench to remove the flywheel after realizing that I would be going through the removal/install process again. In reinstalling it, I was able to use a 12" crescent wrench to engage the flywheel at the center on it's flat edges that act as a two sided nut. The wrench engages the center at an angle since the flywheel sides are the same depth as the center but it was still effective in having enough surface engagement to do the job. I put a shop rag in between the flywheels' edge and wrench handle as a buffer so as not to mar it in any way. I just rested the crescent wrench on the footpeg to brace it while I torgued it to spec.

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  • dmvmechanics

Posted November 21, 2007 - 03:44 PM

#44

do you have to do anything as far as tuning?
how does it run?

  • Krannie McKranface

Posted November 21, 2007 - 06:52 PM

#45

Wow, what a saga. I have been thinking about this idea for a while, and just ran across this thread.
So, the main issue is that the company doing the turning turned off to much in a specific area, is that right?
Why not just get another flywheel and get it done correctly, rather than try and reinvent the wheel...?

  • Thumpage

Posted November 21, 2007 - 08:09 PM

#46

Krannie,

You are exactly right. I intend on doing just that. This is where the behind the scenes story has a little friction in it at this point. It is all about who is responsible for providing a new replacement and I don't think it should be me, if you get my drift. I am going to be sending my flywheel back to the shop since the owner wanted to see it again for himself.

  • Thumpage

Posted November 21, 2007 - 08:26 PM

#47

do you have to do anything as far as tuning?
how does it run?


There is no tuning involved with a lightened flywheel mod. It is usually a simple, straight forward mod to gain more throttle response and quicker rev buildup once you find a shop that can & will do it, properly.
It is mainly for motors that have pre existing heavy flywheel, crank assembly, etc..
How does it run?,..please read the previous few threads, it doesn't run hardly at all yet.

  • ToXicD

Posted January 13, 2008 - 05:44 PM

#48

hey thumpage, did they machine off the back of the magnet or the the front?? if it is the front i was thinking maybe you could rotate the pickup so it picks up a little sooner to compensate the loss of the length of the magnet. it would be like advancing the ignition but since the magnet is shorter it would be just putting it like normal. if it was taken off the backside then that just means its not getting a long enough spark, which i dont think is happening. i believe with the loss of magnet in the front your ignition has been retarded to the point of extreme detonation which is why it will not run.

i have asked about this and havnt gotten much of a response, but i plan on machining an adjustable pick-up holder with slots where it bolts up so you can adjust the ignition advance by just moving the position of the pickup :banghead:

  • JMC

Posted January 14, 2008 - 08:02 AM

#49

I did this mod on, of all bikes, a KDX 200. I wanted a bit more snap like a 125. I chucked it up on a lathe and started turning it down. Not sure how much I took off weight wise but I removed about half of the thickness. Very happy w/the results. I however did not re balance it. I figured since I was taking off the same amount all the way around on the outside it would not throw it off. I ran it that way for 2 years, no problems. Maybe I got lucky? Just thought I would put my 2 cents in. Bet I would love this mod on my xr600 or 400!

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  • hulagun66

Posted January 15, 2008 - 01:33 AM

#50

There's lots of things can go wrong on a bike... I wouldn't be too quick to blame the place that lightened the flywheel.

Unless you think they dropped it.

If no metal was removed from the front or back edge of the trigger (raised up part on the rotor) then the timing hasn't changed any. It's the jumps at the end that the sensor reads. You said the shop removed a sliver of metal from the side (not end) of the trigger. So long as the sensor pickup is over the trigger, with correct air gap, it should work. Unless you messed it up by moving the pickup around.

Bike starts (easily?) and runs, so base ignition timing is close and ignition is obviously working. That tells ya the sensor and the trigger are prolly OK.

My best guess is in all this work your flywheel became demagnetized, which is supposedly easy to do. Just dropping it or knocking it hard can supposedly ruin it. It would also explain why when you tried the flywheel on another bike, that bike wouldnt run right either. Ignition may not be advancing properly because it isn't getting enough voltage.

I havent tried it but someone once told me if the flywheel will pick up a regular hammer the magnets are fine. Not very scientific but there ya go!:banghead:

Good luck and keep everybody posted.

  • ToXicD

Posted January 15, 2008 - 05:12 AM

#51

Good points hulagun, I was thinking they would really have to take off a large chunk to throw off the timing that much not just a sliver.

  • boost 3

Posted January 15, 2008 - 11:06 PM

#52

I think i now the problem!! Just where they rebalace the weel they have cut away some metall that the pikup sensor can read and mess upp the timing!!
Weld that part back and the motor is running,, (Just a wild gess)!! I am doing this mod myself, but i am not"" cut any metall in line of pikup!!

  • Thumpage

Posted January 16, 2008 - 10:58 AM

#53

Thanks for the input from the last few posts. Boost 3 just might be on the right path with his thought. I sent the flywheel back to the shop that did the lightening work for them to inspect it again. The owner said that the additional balancing cutout that was milled away from the material inline with the pickup was most likely the cause. It was told to me that the stator pickup could be additionally signaling from the sharp edges and/or deviation of the cutout. In essence, the cutout would be creating a second timing signal.
I contacted the shop that did the balancing work and explained the situation and had the lightening shop send the flywheel to them. I was told by one machinist at the balancing shop that he had not seen a flywheel balanced like that before and did not know why it had been done that way or who it was that had done the job at the time. The guy, Kevin that had handled my service order before, did not work there anymore.
What they ended up doing as requested by me, was to mill down the remaining center band of material that is inline with the pickup so that there is no deviation in height or edges to create another signal. The center of the flywheel inline with the pickup should now be the same as either side of the pickup where the flywheel was turned on the lathe. Hopefully they were able to do the job without cutting into the front or back edge of the flywheel pickup at all. Of course they know this is critical but knowing and successful execution can be two different things, (Just like the little flub that was made by the shop that lightened the flywheel when they cut into the side of the pickup and the previous *possible* balancing mistake we are talking about from the shop that did the balancing work).
I am hoping that the milling work was done successfully along with the idea or fact that the cause was due to the cutout from the previous balancing work. On the upside, if all has gone well, is that the flywheel should even be a little bit lighter now. I will have to re-weigh it when I get it back. The shop had already had it packed up last time I spoke with them and I had failed to ask them to weigh it for me afterwards.
The shop had finished the milling just a day before I left for a riding trip to Glamis that was from Christmas thru New Years. I took another bike of mine but had wished to take the 650 also. I told them to hold onto it until I got back. I have yet to call them to send it out and should do it today now that I finally checked in on the forum and noticed this thread. It has been very very busy for me after getting back...

I will keep everyone posted on the results when I get it back.

  • boost 3

Posted January 22, 2008 - 01:28 PM

#54

Now i haw lightening my flywheel..... 1866gr oem and 1100 shaved and borred ..I haw shaved away all the outherring away and weld the centrum!!
Now it ripping:crazy:http://www.sporthoj....=171292&page=35

  • Thumpage

Posted January 30, 2008 - 10:38 PM

#55

I can't read the forum link but Whoe!, :ride: . That is some serious material taken away from the back of the flywheel. Especially eliminating the rear riveted weight and rewelding the center piece on, (from what it looks like). The rear of the flywheel looks like swiss cheese, :worthy: :blah: . If you are confident that it will hold together, then I guess I will say go for it,.. ?:busted:? Was it rebalanced? If not, I would have to definitely reccommend having it done with that flywheel. Have you seen others done that way? I myself have not seen anything close to that being done. The bike must surely rev faster.

  • Thumpage

Posted January 30, 2008 - 11:41 PM

#56

Alright, here is the latest news. Problem solved!
I received my flywheel back from the balancing shop. 'Boost 3' was correct as was Jeff @ Procycle, regarding the previous balancing cutout creating a second signal or maybe termed a binary ignition signal which caused the whole problem. The balancing shop, (Crank Works) milled off the remaining center band of material inline with the pickup to eliminate the cutout. They did this for free. This took basicly another 2ozs. off. The total weight taken off now is just a hair over 10.5 ozs. lighter than stock.
The shop did leave a little material edge fore & aft of the pickup, maybe because they were being prudent of not wanting to accidentally cut into the pickup at either end at this point. From what they said, they rechecked the flywheel balance and it showed to be nearly perfect without having to drill any more holes.
I did go ahead and file down the remaining edges left on either end of the pickup,(Just to reiterate, Not the pickup edges themselves, just the material edges left over on either end of the pickup) to a 45 degree angle, anyway, just to be extra thorough.
I have only run the bike in the garage at this point and will say that it does noticably rev quick. I do also think that it seems to run down a bit quicker also after snapping the throttle open/closed. With less mass on the flywheel there might be a little more engine breaking effect going on. ???
In any case, the bike sure sounds lively with the quick free-revs. Here are pics of the end result.

The center band milled off, showing the balanced area.
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2 Pics of the pickup area showing the material edge left on either end.
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Pics of the pickup area after I filed the remaining material edges to a 45 degree angle on either end of the pickup.
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Next, the test ride. More to come.

  • boost 3

Posted February 01, 2008 - 04:02 PM

#57

I have no problems.. It run very fine..8000v all day! I am going to milling away the center band also!! 60g lighter 29,5 oz lighter He, he. And yes i have weld the centrum and then shaving away all the hevy shit. I have never seen any like this!!! Now i am going to milling and drilling the cluch to the limmit..........!

  • Krannie McKranface

Posted June 17, 2008 - 09:03 PM

#58

Alright, here is the latest news. Problem solved!
I received my flywheel back from the balancing shop. 'Boost 3' was correct as was Jeff @ Procycle, regarding the previous balancing cutout creating a second signal or maybe termed a binary ignition signal which caused the whole problem. The balancing shop, (Crank Works) milled off the remaining center band of material inline with the pickup to eliminate the cutout. They did this for free. This took basicly another 2ozs. off. The total weight taken off now is just a hair over 10.5 ozs. lighter than stock.
The shop did leave a little material edge fore & aft of the pickup, maybe because they were being prudent of not wanting to accidentally cut into the pickup at either end at this point. From what they said, they rechecked the flywheel balance and it showed to be nearly perfect without having to drill any more holes.
I did go ahead and file down the remaining edges left on either end of the pickup,(Just to reiterate, Not the pickup edges themselves, just the material edges left over on either end of the pickup) to a 45 degree angle, anyway, just to be extra thorough.
I have only run the bike in the garage at this point and will say that it does noticably rev quick. I do also think that it seems to run down a bit quicker also after snapping the throttle open/closed. With less mass on the flywheel there might be a little more engine breaking effect going on. ???
In any case, the bike sure sounds lively with the quick free-revs. Here are pics of the end result.

The center band milled off, showing the balanced area.
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2 Pics of the pickup area showing the material edge left on either end.
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Pics of the pickup area after I filed the remaining material edges to a 45 degree angle on either end of the pickup.
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Next, the test ride. More to come.


Do we have test ride results?

Also, I am still confused: leaving a centerband the width of the trigger was causing the problem? I would think it would work like stock that way.





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