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Using 450X 5th gear in a 450R (2008)

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Searched a bit and didn't see anyone trying this:

 

I know the CRFs only makes a wide ratio gear set for the 08 450R, but can I just install the 5th gear set from an 08 450X into my 08 450R? Using HondaDirect.com, I can see that the two gearboxes use identical sets of parts (same number of gears/bearings/etc) but obviously the 450X uses different ratio gear sets for every gear.

 

If I check the Honda part numbers, I can see that the 450X uses different shifting forks and drums than the 450R - but what is really different? Don't the gears have to move the same amount if the transmissions (main shaft/counter shaft distances) are the same between the two bikes?

 

If all the 450X shifter parts have to swapped over, then I think the total parts bill will be around $250 - including the 5th gearset. Still cheaper than the $500? CRFs only WR gear set - and I think the 450X 5th gear is taller.

 

The intended use for this bike is a street legal dual sport - so I want a nice tall 5th gear to keep the revs down. According to CRFs only gearing calculator, the 450R already has a smaller wheel sprocket than a 450X - and I'm hoping the 19 inch rear wheel buys me a little taller gearing compared to the 18 inch on the 450X.

 

Am I barking up the wrong tree here - has anyone else done this? I have to split the cases anyway to repair a trashed crank - so now's the time to install new trans gears.

 

Thanks in advance for your advice.

 

Jim

450R tranmission.gif

450X_trans.gif

Edited by F1Jim64

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The 450X's 5th gear is only marginally taller - .826 vs .909. Only about a 9% difference, which would only be a few hundred RPM lower at cruising speed. CRF Only's is .76:1, offering a 20%+ difference, which at 5000 RPM, would knock you down to almost 4000 RPM.

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.826 vs .909 is a pretty big jump and would be worth the cost and effort to me to try. You don't want too big of a change from 4th, either.

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The case width is a bit wider on the 450x, thats why they use different transmission main & counter shafts. Mainshaft on the 450x is 13t and the 450r is 15t. I doubt the gears will swap between the bikes.

Edited by nzgsr

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I know the main shafts are different - isn't the first gear actually cast into the main shaft? It looks that way from the exploded parts diagram. That would make the two shafts different for sure.  And yes the part numbers are different for both shafts, but does Honda sometimes use two different part numbers for the same actual part?

 

And I thought the 450R and 450X engines could interchange between frames - is the 450X case really wider ?

 

Also saw a post that said a 97? CR250 two stoke 5 speed gearset would actually fit into a 450R case - and it was wide ratio - now that would really be Honda re-using a design...

Edited by F1Jim64

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This post says that the 450R and the 450X engines will interchange in 2008 with just a change of the upper engine mount:

 

https://thumpertalk.com/topic/1029476-crf450x-motor-fit-into-the-crf450r-frame/

 

That tells me that two engine cases/transmissions must be very similar or even identical - I know the 450X will have a different casting for the electric starter, but if the lower mounts are the same then the gearboxes must be same width ???

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I've read that the case inside dimensions are different between the X and R to accept those larger gears. I've researched this option as well. It seems the best option (from what I've read up on) is to find a complete tranny from an 01 CR250 and retro fit it in the 450R. Or spend a ton of money on the CRF's only kit.

 

Or you can do like I did and just gear the thing to the moon to get you by. I'm running a 14/38 and I'm maybe going to try a 15/38 in the spring. You definitely have to have good clutch skills to slip that gearing out from a stop. Was a definitely learning curve for me (not used to letting it out that slow). I wish I would have had more seat time on the bike (needed a rebuild shortly after I bought it) before I rebuilt it or I would have done the 250 tranny mod while I was in there but it's too late now I'm not going through all that work again on a fresh motor.

Edited by CarGuy7a

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Thanks Carguy - yeah, I know I can try to get some "highway" gearing by adjusting the sprockets, but I didn't think about the impact on first gear launch. I know nothing about Rekluse clutch systems - would it help with launch if I use 14/38 gearing?

 

I'm going to do some more research on the CR250 trans - the post I found said that 91-97 CR250 parts would fit. Does anyone know the gears ratios for that CR250 gearset? I assume I would need everything - shifter forks, drums, and all the gears?

 

Thanks people !

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Are you running a Rekluse or just a normal clutch? Either way gearing it 14/38 makes first gear very doggy on take off so you have to ride the clutch out alot more than normal and by the time you get the rpms up enough to start shifting, you're in 5th doing 50 before you know it. In 5th gear I'm running about 6000 RPM at 60mph and still quite often catch myself trying to shift into that non existent 6th gear . So realistically it's still geared too low. I'd like to have it around 4000rpm or so but that would require modding the tranny gears to a wider ratio. If you are running a Rekluse and go to that 14/38 gearing you may have to do some tuning with it to keep it from engaging to quickly and too firmly to keep from stalling the engine.

 

Yeah you need the whole tranny setup, shafts, gears, forks, drums. Actually I believe the tranny in the CR250 is identical from 89 - 01 at least all the gearing charts I've found says 89 - 01 and the ratios for the tranny are as follows,

1st 1.800

2nd 1.471

3rd 1.211

4th 1.000

5th .870

 

The 450R is

1st 1.800

2nd 1.470

3rd 1.235

4th 1.050

5th .909

 

So really it's only opening up 3rd through 5th which is what we need for street running while keeping the final drive gearing somewhat reasonable without going huge on the front and tiny on the rear.

 

Here's the link I found about putting a CR250 trans in a 450R.

https://thumpertalk.com/topic/536170-cr250-trans-in-a-crf450r-whos-done-it/

Edited by CarGuy7a

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Nope no Rekluse clutch yet. But I could put one in if it would help from stalling the bike while putting around off road. This thing will be a barely street legal CR with knobbies. Hoping first thru third are nice and low. Then need 4th and 5th for street. Would be real happy if I could buzz 65mph without killing the motor. It will be a 3mm stroker crank so hopefully that will give me some low end to pull the lower final sprocket ratio.

And thanks for the CR250 links . eBay shopping ahead..

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Nope no Rekluse clutch yet. But I could put one in if it would help from stalling the bike while putting around off road. This thing will be a barely street legal CR with knobbies. Hoping first thru third are nice and low. Then need 4th and 5th for street. Would be real happy if I could buzz 65mph without killing the motor. It will be a 3mm stroker crank so hopefully that will give me some low end to pull the lower final sprocket ratio.

And thanks for the CR250 links . eBay shopping ahead..

 

Well with the CR250 trans having that higher 5th gear ratio you may not need to gear as high as I am on the sprockets it's just something you'll have to play around with. If my stock engine 07 will pull 14/38 a stroker shouldn't have any problems at all. Plus what will help if you are running knobbies you won't have to go that small on the rear wheel sprocket due to the height of the tires. I'm running 17inch Warp9 SM wheels with pilot powers so just by me putting those smaller diameter wheels/tires on it's like going up in teeth on the rear gear right off the bat without changing anything.

 

Sounds like you'll have a good setup though dual sporting it with a CR250 trans and knobbies if you're just going to do light road running between trails. I pretty much have mine setup strictly on road right now that's where I'm having my gearing problem (the bike just isn't made for the road but I'm trying to make it that way), then when I switch to dirt trim I just go ahead and swap the gears while I have the wheel off.

 

Make a thread though with pics of you putting that CR250 trans in (if you can) and let us know how it works I'm very interested. Good luck on your build.

Edited by CarGuy7a

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