Lightening flywheel on the XR650R in progress.


57 replies to this topic
  • Thumpage

Posted January 28, 2007 - 08:08 PM

#1

I thought to bring this up since it has been briefly mentioned on the XR650R Vs. CR500 thread a couple days ago about it's most likely effect,(on a 680cc modified bike anyway). I am currently in the process of having my flywheel lightened and then balanced. My bike is a internally stock motored bike but has a full exhaust system, Edelbrock, opened up sidecover, high flow airfilter, etc.. The thought was to get even more response from the bike, quicker rev build-up and hoping possibly at least a touch more top end without getting into the head & cylinder. Talking with a few people the XR650R should definatley have more response but without any real concern for stalling and the like. It is said the XR650R piston& crank assembly is already heavy enough even with a lightening flywheel that it will really never have that kind of problem. It will be more responsive but not so light that it would have major issues on the trail. It is said any comparisons to CRF450Rs or even CRF450Xs and such are just at the opposite end of the spectrum in characteristics. Hopefully it should be a sort of best of both worlds, a good amount of additional response for added thrills but still having that good ol' thumping traction when easier on the throttle. We'll see.
My flywheel weighed in at 4lbs.-1.9 ozs. before the lightening. I will report how much was taken off after it is done. The shop I am using will try to keep the OEM valve adjustment marks on the edge of the flywheel intact just for the sake of it, if possible. I am guessing this may keep a couple ounces left over instead of turning the flywheel all the way to the edge. If it doesn't turn out that this is best they will re-index the flywheel and stamp new marks. I'll soon hear what they did, possibly tomarrow. I will also have pics of before and after when I get it back. Then on to testing it as soon as possible. Whoooo!.....

  • frankstr

Posted January 29, 2007 - 07:01 AM

#2

Thumpage, Welcome to Thumpertalk, :ride:
But , I'd be concerned about affecting the balance when lightening that flywheel, TMO :ride:

  • Thumpage

Posted January 29, 2007 - 06:36 PM

#3

Thanks for the warm welcome. I have read threads here for some time. I finally took the plunge a few months back and joined. Now I jumped right in and posted a couple responses and threads.
At least there is one post in this thread amongst all the reads. :ride:. Tuff crowd, :naughty: .
Actually, I know at least a couple guys from these pages, they just may not know it yet, :busted: .
As for the balance of the flywheel, it is set to be rebalanced after the lightening is done as mentioned in my initial post. In fact the lightening itself was done today and sent to be rebalanced. The flywheel now weighs 3lbs.- 9.4ozs. which makes the flywheel basically 8.5ozs. lighter.
The outside was turned, along with some of the back rear portion of the flywheel. Prudent attention to keeping sound structural integrity was in mind with how much was ultimately taken off. Additionally the back plate that is riveted to the back of the flywheel was turned down close to the rivets while keeping enough steel surrounding them for the same purpose. The middle section of the flywheel inline with the pickup remains the full thickness. The leading edge of the flywheel was left intact where the valve adjustment line-up marks are.
The flywheel to begin with in stock form was not as heavy as it was speculated to be to start with. The amount taken off was also not nearly as much as what I have heard has been the case. Only just over half of what has been said to be taken off elsewhere, at around a claimed pound. As mentioned above, there is at least a bit more that can be taken off with more time and labor, such as maybe in the area inline with the pickup, not to mention other little areas and/or possible additional thinning in the main areas. Some additional weight that could be taken off would be close to the centerline of the crankshaft and probably not amount to much difference compared to the additional weight taken off and the time, labor & price to do so. That is what the shop I had doing the work explained to me anyway.
With the way mine was done, I and the shop were comfortable with this end result. The price of the lightening seems very reasonable at $55 including shipping from them. Rebalancing will be $20.
Well, for those that don't like reading long posts, sorry, :ride:. With all my scouring for information I tried doing before setting my mind on doing this mod, the info was limited. I thought to share more detailed info about this modification specifically related to the XR650R. :ride: :applause: More to come. Can someone tell me how to attach pics into a post? Is it simply cut and paste from Photoshop? Thanks.

  • bcone

Posted January 29, 2007 - 08:21 PM

#4

Try the search feature for more info on pics.
Basically you have to post them at a host site and then "go advanced" and link them. It will ask for an Url and you just cut and paste from the other site. There are several sites to host pics. Try Imageshack, I had the best luck with that.
As for few posts, lots of guys seem to be doing "light" engine performace mods such as carbs and pipes, but engine work is a whole nuther ball game and so I'm betting there are fewer out there who have anything to contribute. Look forward to your result. Hope it gets you the snap your looking for.

  • thouk

Posted January 29, 2007 - 09:58 PM

#5

Thumpage,
Which shop did the turning of your flywheel? Thanks, Tony

  • Hondathumper450

Posted January 30, 2007 - 09:42 AM

#6

Please let me know how it turned out. I am the maintenance manager at my factory and we have our own in house engineering and machine shop. The guys would do it for me in a heartbeat and doesn't cost me a thing.
please keep us posted

  • Thumpage

Posted January 30, 2007 - 11:07 AM

#7

bcone, thanks for the info and suggestions for attaching pics. I will look into it so that I will have pics available when I get the flywheel back.
Actually, lightening the flywheel is very easy. It is nearly as simple as changing or having your stator rewound. You just merely remove the stator cover to access the flywheel. You can remove the flywheel with an impact wrench or have the flywheel holder and a breaker bar. Getting it back on you will need the holder.

thouk, The company that lightened my flywheel is Procycle in Oregon. The Owner is Jeff and he is just the nicest guy. I can't say enough about his professionalism. He took the time to discuss with me the particulars of the lightening process, how flywheels can be made different, how the lightening process can differ between flywheels, etc.,etc.. He precisely weighed the flywheel before and after so he could have a record of a XR650R flywheel and give me the detailed info that I was inquiring about. Trailtech will be doing the rebalance work, it is Jeff,(yes, another Jeff) in the technical department that I have talked to and arranged to receive my flywheel and set the work to be done. From reading about the process of rebalancing flywheels, I believe Trailtechs method is the best and most precise way for it to be done.

Hondathumper450, I will follow up with pics and other related info. when it arises. I guess your in-house shop could emulate the process as long as it was for your XR650R and not a 450, as is your handle. The 450 flywheels are on the other end of the weight scale and would need a heavier flywheel if anything for the opposite purpose. I know you are inquireing within this 600/650R forum :ride: but I am just making 100% sure. :ride: . In any case, as long as they don't get to carried away trying to make it too light. The flywheel needs to have enough leftover thickness for it to be able to be rebalanced and also not have any risk of coming apart. There are the magnets sandwiched in-between the outer flywheel layer that still need enough steel encasing them, besides all else. I am just expressing prudent caution for the specific application, :ride: . Cool talking with you guys.

  • Hondathumper450

Posted January 30, 2007 - 12:02 PM

#8

Had a CRF450R and traded it for my now XR650R.

  • Billahjack

Posted January 30, 2007 - 06:00 PM

#9

A cam would go a long way towards more power than a flywheel mod.

  • Thumpage

Posted January 31, 2007 - 05:28 AM

#10

Hondathumper450,
Good choice on making the switch. CRF450s are cool no doubt but the BRP will last you a long time without the same costs, :applause: . Totally different bike for a different purpose of course. :ride:
One thing I failed to provide was to actually give direct links to the companies that are doing the work for me, for reference. Flywheel Lightening work: http://www.procycle.us/index.htm
Rebalancing: http://www.trailtech...rcycle_home.htm

Billahjack,
No doubt a cam will offer more power throughout the midrange and top end. :ride: The flywheel mod provides more response from the power that is there and quicker rev buildup, maybe not literally more power. The power is generated quicker from having less mass to spin up. Other noted benefits and reasons for doing this mod can be 1) the potential cost effectiveness of this modification 2) Those that want added response over and above their Pumper carb & freeflowing muffler or full exhausts, (not to mention added to internal motor mods if you want it more wild). 3) For guys that simply want to keep their internal motors stock and still get some added arm pull. :ride:
I would have to say that I think the flywheel mod really needs a Pumper carb to work to it's full potential but it has been reported to work with stock carbs.

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  • hypersthenos

Posted January 31, 2007 - 12:30 PM

#11

Sounds like a cool idea. Sorry, I skipped this post a few times before reading. I actually like the long, technical posts. Let us know how it turns out. I learned to rewind my stator on this website & found the help here to be accurate & courteous. Hope you have the same experiences.

  • Thumpage

Posted January 31, 2007 - 11:38 PM

#12

Thanks. So far so good, :ride: .

I ran into a bit of a snag. Trailtech CANNOT rebalance the XR650R flywheel. They do not have a spindle that matches the flywheel to chaulk it up on their particular balance machine, :ride: . Chris at trailtech called me right away about it to let me know and explained the matter. He has been a cool guy the couple times I spoke with him. He was the one that was going to arrange for Jeff to receive it for lightening.
I guess since they do not manufacture a heavy flywheel for the XR650R,(since it is not a bike that would need one) they don't have a matching spindle. I wish they could have told me this before I had sent it to them or even inquired about it with them. Oh well :smirk: :ride:
After some scouring, I found another company based in Arizona that produces, services and balances racing cranks & also balances flywheels for the powersports industry. It was hard finding anyone to do this! There are a few offroad companies out there that sell or lighten flywheels for the ATV market. but non of them said they balanced them themselves or new of anyone who did,:ride:. Do they just not want to give up sources without selling their own flywheels or flywheel lightening service? :busted: :applause: :ride: Or they just have a little bias against two wheeled bikes, :naughty:
Anyway, this company I found uses the same or similar dynamic balancing as trailtech but their machines method has multiple holding capabilities or they have different ways of accomplishing the task from what I am told. I guess it doesn't need a specific spindle to hold the flywheel. They said they would most likely be able to do it, It will be a bit more cost than if trailtech could have done it. It will run $45. If they can't do it, no charge for checking it out. I will let everyone know what ends up happening. I am waiting to get the flywheel back from Trailtech and then send it off to this other company. More info. on them when I go through the whole process. So far the guy I talked to was very affable over the phone.
Obviously more to come.

  • porterdog

Posted February 01, 2007 - 06:34 AM

#13

Damn, you are really jumping through some hoops for a 15% change in FW mass. I hope it works well for you- I put a lightened FW in my Miata and it was a *great* mod but the mass change was closer to 45%.

Looking forward to a ride report.

  • Billahjack

Posted February 01, 2007 - 07:05 PM

#14

Hondathumper450,
Good choice on making the switch. CRF450s are cool no doubt but the BRP will last you a long time without the same costs, :applause: . Totally different bike for a different purpose of course. :ride:
One thing I failed to provide was to actually give direct links to the companies that are doing the work for me, for reference. Flywheel Lightening work: http://www.procycle.us/index.htm
Rebalancing: http://www.trailtech...rcycle_home.htm

Billahjack,
No doubt a cam will offer more power throughout the midrange and top end. :ride: The flywheel mod provides more response from the power that is there and quicker rev buildup, maybe not literally more power. The power is generated quicker from having less mass to spin up. Other noted benefits and reasons for doing this mod can be 1) the potential cost effectiveness of this modification 2) Those that want added response over and above their Pumper carb & freeflowing muffler or full exhausts, (not to mention added to internal motor mods if you want it more wild). 3) For guys that simply want to keep their internal motors stock and still get some added arm pull. :ride:
I would have to say that I think the flywheel mod really needs a Pumper carb to work to it's full potential but it has been reported to work with stock carbs.


Hondathumper450,
Good input. Just remember that if you spin up too fast then that manifests in poor traction control. That is partially why motocross bikes used to get heavy flywheels for trail riding. The other reason you want a heavier flywheel is to minimize stalls in tight slow technical sections.

If you have a small displacement motor that stays around the redline, then a light flywheel allows it to rev and accelerate faster. The 650R is more of a chugger when compared to a 250 2-smoke. By this, I mean the 650R goes from 2000RPM to 7000 RPM in about 2 times longer than a 2-smoke does because it has more mass and monster torque. On the other-hand, the 650R has taller gearing which evens out rev build-up versus acceleration so the 2-smoke shifted 4 times while the 650R shifted twice.

Last, a lightened flywheel is advantageous when the motor is changing RPM in situations like motocross where you drag race to every corner, come to a stop then drag race back out again. Maybe the guy racing the banshee needs this. It sounds like his bike is going to be a screamer!

By the way, last week there were 10 hotcams stage one for buy it now on E-bay at about $60 a piece. Hard to beat the power increase to cost ratio on that. Otherwise, its about $160 on the net for a stage 1 or 2.

  • Thumpage

Posted February 07, 2007 - 08:40 PM

#15

Billahjack,

I guess the minor tribulations of this process sounds like more drama than it really is. It didn't take long for me to find the alternate source for rebalancing it. A few more days delay in ultimately getting it done, oh well. Besides, anyone else that may be interested in doing this also, will have it all layed out for them with resources, costs and details covered. That is why I thought to share what could possibly be a cool, easy, worthwhile and unique, (for the XR650R), modification. :censored: Nobody could ask much more than that, right? :applause:

Oh I here you, (By the way, I think you got me and Thumper450 mixed up. :applause: :applause: ) on seeming comparisons to moto bikes but from what has been told to me by the professionals regarding the crank and flywheel, there is just no close comparison. The 650R crank assembly is just much heavier than 450s and other bikes so it should not be negatively effected by lightening it. At least not with the amount that was taken off of mine. As you noted, the 8.5oz (half pound) difference that was taken off is not a big figure anyway in comparison to the overall weight of the flywheel and crank assembly. So really, I don't think the mod will produce unwanted wild wheelspin. I do hope it will achieve just enough to make a noticable difference in extra rev buildup though. Regardless, any weight taken off will help. I can only guess it will still have the legendary tractor pull when needed also. Best of both worlds is what I am striving for :ride: I have thought about installing a hotter cam at some point in the future also... :lol:

  • Billahjack

Posted February 09, 2007 - 11:01 PM

#16

How is it turning out? Does it ride better? I had a RC-51 with a massively heavy crankshaft. The thing I noticed the most was the huge effort it took to go from full left bank to full right bank on turns. I had to both push on the pegs and wrestle the bars over. Anyway, I was thinking that the flywheel lightening might make the direction changes faster on the 650R.

I just put a cam in one of my bikes. Took about 2 hours but I didn't get to ride it yet since I don't want to wake up all the neighbors. I want to get a little bit more wheelie power and top speed.

Cheers

  • Thumpage

Posted February 11, 2007 - 11:16 PM

#17

I don't have the flywheel back yet. It is in the balancing process at the moment. I should hear something of it's status this week sometime.
Regarding the idea of direction changes on the bike with the lightened flywheel I don't know if the half pound would make any difference. A good contributing factor of the lack of ability in changing direction fast on the big 4 stroke singles besides the weight of the bikes or motors themselves, is the Gyro effect of the huge piston and crank assembly all together.
I will be posting as soon as I can as things happen. Pics will be included too.
There is no doubt you will get more wheelie and top end potential with the cam. I should get a little of the extra wheelie potential with the flywheel mod also. More coming soon...

  • Thumpage

Posted February 19, 2007 - 12:13 PM

#18

Just a quick progress report. The flywheel did need to be rebalanced. The flywheel is being rebalanced by Crank Works, out in Tempe Arizona. They have been very busy, so there was a little delay. They should have it done in a couple days. I will have more details then.

  • Thumpage

Posted March 03, 2007 - 01:53 PM

#19

O.K., I got my flywheel back earlier this week. I Just hadn't made the time to take pics and organize them for this post. So now here they are.
I will show them in stages in three different posts. One thing I failed to mention early on, is that the process does require you to have a flywheel puller along with a flywheel holder to get it on and off. I thought I might be able to get the flywheel bolt loose by some creative way to hold the flywheel with a strap tool and hold the rear brake or some other combination,..I was NOT successful. Those bolts are on there! You will need a flywheel holder if you are doing it yourself.
I bypassed the removal step without having a holder from having a buddy from a local Honda shop use a air impact wrench to very quickly remove the flywheel. He air wrenched the bolt loose without needing a holder and also used the air impact wrench with the flywheel puller bolt to pop the flywheel off. It took all of 10 seconds. The flywheel puller bolt is a 20mm x 1.5" bolt.

To reinstall the flywheel I will need to order the Honda flywheel holder so that I can torque it back on to the proper specs. The guys at the shop said they use an impact wrench to install them back on without needing a holder. They explained that you just have to know the tool and know roughly how much or how long to run it on the bolt. Even with trained hands, I'm not that big on the idea myself. Maybe it is not that critical but I want something more controlled and precise anyway. I will order me the flywheel holder and torque it down myself.
Here are pics of the stock flywheel:
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  • Thumpage

Posted March 03, 2007 - 02:12 PM

#20

Now here is the flywheel after the lightening process. I had Procycle leave the front edge intact so that it would keep the valve adjustment marks on the flywheel just for the sake of keeping them. [there is an easier and clearer way to readjust the valves than using the marks on the flywheel,.. but that is another subject.] Like I said, I just had them keep the marks on the flywheel for the heck of it.
You can see on the side view pic, they did not machine the front edge down. They started the cut just back from the edge, leaving a lip to keep the marks. As mentioned early on, the flywheel came out to be 8.5ozs lighter. The next stage was to have it rebalanced if it needed it. A pic of this next stage in the next post...

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