(New & Improved) Stator Install - Stromtrooper Forum : Suzuki V-Strom Motorcycle Forums
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post #1 of 68 Old 02-05-2017, 02:35 AM Thread Starter
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(New & Improved) Stator Install

I had a chance to replace my stator this weekend. Last weekend I replaced my Spark Plugs and tested the stator since my charging system was acting funky. I was able to buy a used stator (with side cover and gasket) for $50 from an old SV racer who had a whole cabinet full of SV side cases with stators. I took the pick of the litter but I was hoping to kill two birds with one stone and find a clean side cover to replace mine as it has the dreaded paint rot but, as could be expected, all the SV covers were race rashed.

If you have seen my past posts you'd know that I can't just work on my bike as is, I like to find simple and cheap ways to improve the design of the components that I work on. As we all know the stator is a weak point on this bike so I considered that a challenge to address when I opened it up for service. Its seems clear that these stators run hot, breaking down the wire insulation and eventually shorts out. The first thing I noticed was how little metal there is on the stator mount built into the crankcase cover. That was a big red flag for me immediately.



While these stators are oil-splash cooled a significant amount of heat is conducted through that mount but it just doesn't have enough meat to draw the heat out of the stator core and coils. If the mount was filled in at the areas marked by the red arrows and silver lines then I think the stators would probably last a lot longer. Since Suzuki won't be recasting the side cases any time soon I thought of a plan-B.

In my business we use thermal grease for mating computer CPUs (that run hot) to a heat sink so I thought a little (okay, maybe a lot) thermal grease can improve the conduction of heat to the case cover and lower the heat load on the stator. Step one was to make sure that the mating surfaces were smooth and mated properly which is important for a good thermal connection. Here is a picture of my new stator, the back side that faces the cover (sorry for the blurry image).



The yellow circle highlights an area where I sanded down some bumps that would have kept the stator core from sitting flush on the mounting surface thus impeding heat flow. When I pulled my old stator I inspected it and found what look like resin gobs and weld splatter in the area where the wires are attached (circled in red). These defects would have definitely interfered with a proper mating of the stator to the mount and increased the thermal resistance in that area so I have to wonder if this is a factor in stator failures. Fortunately, my new stator was clean and smooth in this area. The surface that the rotor mates with on the side case is machined so it was smooth enough for a good thermal connection so I didn't have to do anything to prep that other than clean it with rubbing alcohol. BTW, I used rubbing alcohol to clean all the surfaces of oil before I started.

The second issue I addressed was the mounting bolts. These bolts are M6-1.0x30mm but fully threaded which I didn't like. I thought that a bolt with a shank would be better for conducting heat out of the stator core.



The bolt on the left is an M6-1.0x45mm which has a shank of 20mm which is a tad longer than the thickness of the stator core so I had to add a washer. I eyeballed the clearance of the cap head + washer and it was below coil wires so there should be no interference issue with the back of the rotor. I did have have to file down the washers diameters a bit to fit under the cap so they didn't hang over the edge of the stator ring. I stacked an OEM bolt on top of a washer and used that to mark the place to cut the 45mm bolt. Before cutting it I put on a nut so that after cutting I could remove it and it would chase the threads, then I filed down any cutting burrs and I had a 30mm bolt with a shank. Here is everything ready for assembly.



On the left (yellow circle) I coated the crankcase cover stator mount with thermal grease. I also put a small dab at the bottom of the screw holes to conduct heat from the ends of the bolts but left the threads clean. I used MG Chemicals Silicone Heat Tranfer Compound 860 which seemed to have the right properties, including temps over 200C/400F (the jar, which was $9, is circled in black but you can't read it as I intended. Also, its enough to do about 10,000 stators so I am set for a while... if anyone one wants some PM me). I greased the back of the stator (green circle) that mates with it's mount and put a liberal amount of grease in the through holes (I used Q-Tips). I also greased up the shanks of my custom bolts shown in the purple circle and put a dab on the ends of the bolts, keeping the threads clean. Before assembly I put a tiny dab of blue loctite on the mounting threads just to be sure nothing comes loose. Here it is all assembled and (almost) ready to be installed.



This is after a bit of cleaning with rubbing alcohol to remove the thermal grease that oozed out from all the contact areas when I assembled it and tightened the bolts. In retrospect I think I used too much thermal grease and Q-Tips are probably not the best applicator but I couldn't think of anything else. Also, the final step was to run a bead of black, oil-resistant sealant around the gap between the stator and the case cover. Its circled in green and that gap is not a pressure fit so I was afraid that oil would wash out the thermal grease which does not set like sealant.

Okay, there you go that is my new and improved stator install. As always, use at your own risk, YMMV, benefits may only exist in my mind.
Attached Images
File Type: jpg StatorMount.R2.jpg (66.7 KB, 401 views)
File Type: jpg NewStatorR2.jpg (68.1 KB, 394 views)
File Type: jpg StatorBolts.R2.jpg (63.2 KB, 392 views)
File Type: jpg GreasedStator.R2.jpg (74.5 KB, 414 views)
File Type: jpg StatorReady.R2.jpg (72.6 KB, 394 views)
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post #2 of 68 Old 02-05-2017, 06:57 AM
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I can see the thermal grease being able to take the temperature as it would in a computer application, but isn't the hot oil going to wash it out? I find it hard to believe there will be any grease left before long. I do like the idea of getting the best mating contact possible between stator and cover. When I checked cover temperatures between the stock R/R and the SH775, there was a marked lowering of temperatures with the latter so the cover is definitely drawing heat out of the R/R despite being continuously splashed by hot oil.

Pat- 2007 DL650A was ridden to all 48 contiguous states. I didn't quite make it to 17,000 miles on the 2012 DL650A.
Nicknames I use to lessen typing, Vee = 2002-2012 DL1000s. Vee2=2014+ DL1000s. Wee = 2004-2011 DL650s. Glee = 2012+ DL650s
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post #3 of 68 Old 02-05-2017, 09:06 AM
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I like the concept. Not sure about the thermal grease, for the same reason as greywolf. I could see going a step further and filling in the magneto cover under the stator with JB Weld. Then machine the surface to match what is there from the factory machining. This makes sense, the magneto cover would pull heat evenly from all the poles. Aluminum is a good heat sink and if you can get the heat into the cover, it would have to make the stator run cooler. Might be one of those "fixes" that is hard to document as an improvement, but I certainly give it a thumbs up!

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post #4 of 68 Old 02-05-2017, 10:07 AM
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At work we use indium metal foil pieces to increase thermal conductance between copper parts in cryogenic vacuum pumps. It flows into the microscopic surfaces as the pieces are bolted together. Indium melts at 313 F.
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post #5 of 68 Old 02-05-2017, 10:18 AM
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Thermal grease works by filling in microscopic surface irregularities and maximizing surface area contact.
Nothing wrong with trying it but not a clue how it will react to a hot oil bath.
A more effective way to lower the heat is to simply reduce the load. If you look at the series regulator thread it's been talked to death.
Bottom line the stock shunt regulator results in maximum current (= heat) at all times.
I just had my stator replaced under the recall and still plan on replacing my regulator since it will reduce heat and increase reliability.
Add all LED lamps and the electrical load should be minimal.

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post #6 of 68 Old 02-05-2017, 02:17 PM Thread Starter
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Oil washing out the thermal grease is probably not a problem. The mating surface between the stator and the side case is under a lot of pressure with 90 in-lbs on the bolts, it would take a really focused jet of hot oil to impinge on that gap. As Brojon mentioned, thermal grease just fills in the microscopic gaps between mating surfaces which is another reason I shouldn't have used so much, it only takes a little grease to span these gaps and I doubt oil wash could even get into the spaces. The grease in the rotor through-holes is probably safe from oil wash as that area is completely sealed by the bolts. The annular gap between the case and rotor core is open and probably would wash out which is why I sealed it with gasket seal.

For people installing new rotors I think checking the mating surfaces is probably a minimum step to help cooling even if they didn't want to go down the thermal grease path or mess with custom bolts, etc. Thermal degradation is highly non-linear and correlated with peak temp and temp cycling (hot/cold) so even a small decrease in peak temp could translate into thousands of miles of stator life. A bump or defect on the mating surfaces could really impact stator life whether using thermal grease or not. Here is a pic of my old stator.



You can see all the crud just below the bracket mount and it would create a gap and impede heat flow. This is in a critical area because most stators coils fail near the top of the stator where (presumably) there is less oil cooling compared to the bottom coils. My SV stator had bumps on the mating surface but they were down at the bottom so probably not as critical but I wanted a clean connection all the way around. At 85K miles I don't know if this is the original stator or a replacement, I suspect the latter as the owner admitted she "had electrical problems" with the bike but the service records were sketchy so I could not confirm. It would be good if someone could do a before/after side case temp test using IR as proof of concept that the treatment is helping. It is interesting that with a series R/R the temps should go down but with a OEM shunt R/R, after thermal grease treatment, the temps should go up.

I've been thinking about that and, per Myth Busters, anything worth doing is worth over doing! So continuing this line of thinking I want to somehow mate an LED heat sink to the crankcase bolt access cover. Here is what I have in mind.



These LED heat sinks come in a variety of sizes and I am looking for one about 50mm dia and maybe 20-30mm pin fins (so it doesn't stick too far out from the side case). I have to figure out how to bond/bolt this to the access cover and I think that would really drop the stator temps, so much so that I'd be fine with OEM shunt R/R.
Attached Images
File Type: jpg OldStator.jpg (34.3 KB, 337 views)
File Type: jpg HeatSink.jpg (92.7 KB, 329 views)

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--------------------------------------------------------------------------------------------
Current: 2007 V-Strom DL650 ABS Silver
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Last edited by dmfdmf; 02-05-2017 at 02:26 PM.
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post #7 of 68 Old 02-05-2017, 03:59 PM
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I doubt thermal grease would make a very good gasket sealant. I would be very surprised if it lasts.

Pat- 2007 DL650A was ridden to all 48 contiguous states. I didn't quite make it to 17,000 miles on the 2012 DL650A.
Nicknames I use to lessen typing, Vee = 2002-2012 DL1000s. Vee2=2014+ DL1000s. Wee = 2004-2011 DL650s. Glee = 2012+ DL650s
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post #8 of 68 Old 02-05-2017, 05:21 PM Thread Starter
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Quote:
Originally Posted by greywolf View Post
I doubt thermal grease would make a very good gasket sealant.
I agree but where is it being used as a gasket sealant? Its a surface treatment.

At least we agree that stators and crankcase mounts should be free of defects that interfere with proper mating and thus inhibit heat conduction.

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post #9 of 68 Old 02-05-2017, 06:28 PM
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It is subject to the same conditions as a cover gasket would be. Hot oil cuts through practically all things not specifically designed to stop it.

Pat- 2007 DL650A was ridden to all 48 contiguous states. I didn't quite make it to 17,000 miles on the 2012 DL650A.
Nicknames I use to lessen typing, Vee = 2002-2012 DL1000s. Vee2=2014+ DL1000s. Wee = 2004-2011 DL650s. Glee = 2012+ DL650s
See http://www.stromtrooper.com/general-...nicknames.html

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post #10 of 68 Old 02-05-2017, 08:07 PM
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I think it may get washed out, but should handle the temps. We use heat transfer compound on laminating rolls for the heat elements.

I've tried it on the R/R mount to the bracket before.

https://www.mcmaster.com/#heat-trans...ounds/=1688wkb

You could fasten some sort of heat sink onto the outside of the stator cover. Probably get damaged in a tip over though.

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Last edited by Dave Tysdal; 02-05-2017 at 08:11 PM.
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