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Interesting 06-08 chassis mod

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Years ago, I remember being impressed when I installed the 08 engine mount mod on my 06. Two weeks ago, I was intrigued to hear Chad Reed talking in an interview about testing different torque values on bolts holding the cylinder to frame "hanger" plates on his '11 CRF450 to change the turning behavior, and him being very surprised with the results. In the past year I've noticed many pro teams with any bike brands modified these hangers compared to the stock items. Eg. All the current Pro Circuit KX250Fs have substantially cut down hangers.

So in search of even more frame flex on my 06, I modified my engine hangers. I took a lot of the width out of them, plus I only torqued the bolts to 20nm each (with some loctite). I'll post a photo when I can.

My altered plates will still cope with the counter sprocket torque which pulls the cylinder aft under power, but the real change is that they should allow the main spars to bow outward a bit more, and also allow more twisting thru the head stem.

Anyway the results seem really positive on my first test ride. Today I rode for about 3 hrs in total on a tight wet sand track. Traction was pretty good, and I have good settings for that track. Some ruts were deep and well defined and easy once the bike drops into them, and my bike always feels great in those so I'd say no difference. But some tricky corners were a total mess with many lines possible, and inconsistent arc/radius were common. Normally I find my 450 is a real handful on this track, but today I could put the bike anywhere, open lots more throttle and ride for longer. I need to go out and test in more conditions because perhaps today I was just feeling the force or something.

I also rode on a wet grass track which has a few moderately deep 3rd gear arc ruts, and I felt like I didn't really need to steer thru those. On small woops I felt more comfortable than usual too.

Perhaps what I felt today had a lot to do with those conditions. I know my memory aint great, but considering cornering speed and my trust in the bike, I think I had my best ride ever int he past 4 years. My only setup change were these engine hangers.

It might be a winner. Any 06 to 08 KX could do it. The 09 to 11 hangers are already trimmed down, more on the '11 I think. Torque on the bolts has to be a big factor too.

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I think the '11 head stays are stamped steel rather than the thick aluminum pieces used in previous years. I don't know if they fit the earlier bikes but might be an option to try.

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I tried different torque settings on the trippleclamps to ad more flex and experiment with fork ridgety. This also made some differences.

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heindl440, I've got a set of 09 triples. No idea how the flex differed to the stock 06-08 triples, but the lower offset is much better. I torque the triple clamps as loose as I can to avoid twisting up the front in mild crashes. That's about 20 on the bottom and 25 on the top. I dont want to go looser or tighter than that.

Kroynon, Interesting if the '11 plates are thinner steel. They looked like alum in photos I saw. I trimmed down mine to have the same profile as those on the '11. Always fun to look at chassis mods as they appear on pro team and new model stock bikes. In photos I saw some head stays that were not the usual gray alum on Clement Desalle's 2010 RMZ450 GP bike, but no clue if he raced with them.

I thought about getting some made out of stainless steel. Had the same thought when I did the front engine mount mod. But I opted for the thick alum parts mainly because it was a zero cost 1 hr hobby mod with a grinder, file, sand paper and some metal polish. Also because in highly conductive alum, they act as real nice heat transfer paths. My frame's main spars get pretty hot at times, so it's good engine cooling. Lastly I thought the thick alum parts give more load bearing surface on the bolts, which I thought was good for coping with the countersprocket torque on the whole engine - without needing the bolts torqued real tight.

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I thought about making some engine mounts out of carbon fiber and epoxy resin.Since its a flat surface you could press the layers to squeeze out the extra epoxy and make a strong piece.The upper hanger mount would be a bit trickier but still easily doable.Good place to save weight,and a significant amount too.You could use CF pipes cut to size as spacers to get the flex.

Only problem I could think about is heat dissipation,although I dont think the heat dissipipaed by the engine mounts is even significant.

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MCL, The alum hangers are not heavy once cut down. Not enough to justify carbon+epoxy IMO. The thing is, it's not about the weight (even though I love saving weight). It's about flex, and for sure more flex is better on the front mounts, and it seems the same is true for the hangers.

You could make some thinner carbon plates to get some flex, but then you'd have problems with not enough load bear surface on the bolt shafts.

IMO the heat dissipation via the mounts is very significant - if you ride in hot weather. Which probably means a dont care in Finland! A few weeks ago I was riding in 32C air temps (not super hot), on a tight track with little wind, when I stopped the bike, my main frame spars were too hot to touch with bare fingers for more than one second. I'd estimate burned finger tips in about 3 seconds, and the frame spars were about 80C.

Another problem with carbon mount plates would be corrosion. carbon+alum forms a battery. Once the carbon starts to "eat" the alum, the reaction progresses very fast.

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When MXA does a report on factory bikes, they almost always mention how the engine mounts are torqued lighter, but checked after each ride.

How hot does it get where you used the Loc-tite? Be sure to stay on top of it in the beginning, so they don´t vibrate loose.

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D-K, all the mount bolts eventually come up to full cylinder temperature. I've used blue loctite on my exhaust midpipe mount bolt, and muffler bolt and it lasts for a while. But good point, and I'll keep checking they dont come loose.

My lower front mount plates have always been torqued quite loose, but I put epoxy resin (mixed with micro fiber) on the front bolts to remove all slop and also prevent anything coming loose. And it's never moved. If I do need to remove the case from the frame one day, then the epoxy bond on those mount bolts can be broken by applying a large soldering iron tip on each bolt.

Interesting about those comments by MXA. I never noticed that.

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Here are some pics of my trimmed down cylinder hangers/mounts. Not super slim, but I took a fair bit off, and they are only torqued to 20nm each.

I'll test again tomorrow. Hopefully drier conditions this time. Shall see.

20110215-P2152516.jpg

20110215-P2152517.jpg

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Thought about doing that too. Just decided to take it one step at a time. Also a little cautious about high loads during big hits.

I'd like to assume the frame is massively over engineered for the usual stresses.

What can you say about the handling - with them completely removed?

I didn't really learn anything last test ride. It wasn't too wet that's for sure. But it was 100F (38C) in the shade and I wasn't feeling the force that's for sure. Actually I wore myself out riding a '10 CFR450 for maybe 45mins. Learned bit on that, but then I was physically stuffed/ruined for the rest of the day.

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