400ex tranny conversion

[monkeyballs]

Ok I know this sounds crazy! But I wanted to know if its possible to convert a 400ex tranny so that its similar to a 450 tranny. Like put new gears with diff... I need that top end torque. I am just starting mx and I need gears that are not as long but still have the same speed.. Any one ever attempt this and how did it turn out any problems?

[honda400ex2003]

i suppose you may be able to but you would have to get a whole new set of gears to change them all. it would be a ton of work. why not just get a 450 motor to put into the frame? That would be the easiest way i guess. i know they do it on the sleds but i dont know if you could find a whole gear set for the 400's in a higher ratio. steve

[monkeyballs]

Sleds (clutches) and quads (Cars) massive diffrence. And sleds only have 2 gears and a primary and secondary clutch wich is a completaly diffrent set up thena tranny.

Then the reason for this is becaus I live my 400ex. I wanted to compare prices.. I realy want a 450 but then that requires me to sell my 400ex and wait a while to finde a good deal on a 450. And I put to much money into my bike. It should be bullet proof.

-Hc stg 1
-yoshi pipe full system
-K&n air filter with pre charger
-416 bore (87mm)
-wiseco light weight piston 11:1
-Miled port and polish
-New timing chain
-New timing chain guides
-New tusk clutch
-New clutch basket (hinston)
-All new gaskets and o rings
-clutch leaver 909
-razor 2's front
-holeshots back
-Running no air box lid
-FINALLY! TO MUCH TL&C

[honda400ex2003]

it was a quick comparison for reference. It is a bigger difference like you said. i would still find a 450 if you are really bent on getting one. you can find some cheap ones around for the older ones. steve

[Honda#4]

If you are planning on buying a 450 dont even worry about the gears for a 400 it aint worth it.

[1krazyquadridr]

I did something simiar to what you are talking about. I did a direct swap of a XR400 trans into my 400ex. The ratio's are different and more suited for MX. I can now start a race in 1st rather than 2nd. Let me know if you've got any other questions.

[katch26]

does the ex motor have trouble pulling the dirt bike tranny? stock sprockets?

[monkeyballs]

Originally posted by 1krazyquadridr
I did something simiar to what you are talking about. I did a direct swap of a XR400 trans into my 400ex. The ratio's are different and more suited for MX. I can now start a race in 1st rather than 2nd. Let me know if you've got any other questions.
That sounds awsome! How did all that work out? Did it also work verry well? Did you have to match up the years? Or how does that work. Finally, do you have any clue what the gear ratios are and what the shift drops are? Thaks :D

[1krazyquadridr]

Here are the comparative gear ratio's
400EX XR400
1st 2.916 2.62
2nd 1.937 1.84
3rd 1.473 1.40
4th 1.181 1.12
5th 1.00 .93

So as you can see I don't have as low of a first gear, a more even spread throughout the gears, and higher fifth gear. It was really a total transmission swap. I bought a junk XR400 motor and just swapped everything from the tranny over, pretty simple actually. If I remember correctly I had to change one bearing because one of the XR's tranny shafts is actually slightly larger in diameter. It works great and gives the bike much better gearing for MX.

[monkeyballs]

Omg! Thats almost perfect for mx! I just calculated the shift drops for both and here is the outcome im suprised.


400ex:

Rpm shift drop

1 2949 1490
2 4439 1399
3 5838 1443
4 7281 1319
5 8600

For every one to understand.. This is the final drive at the rev limiter *8600rpm. Then shift drop from 5th to 4th its 1319... And for first gear.. Its simply for first gear its the rpm..

XR400:

Rpm Shift drop

1 3282 1391
2 4673 1469
3 6142 1536
4 7678 1569
5 9247

Look at the shift drop from 5th to 4th! That would be some serious torque. Thought almost to much. This sounds like a well worth the while mod. I must thank thee for posting your positive info :D. Exactly what I was looking for! And it wont cost me any where close to a 450!!! :D Do you have any pics or any other info I need to do this? And from what I hear the xr trannys cant take mx riding (for some reason it wont shift when its realy hot.. Passed 3rd gear) You have any problems? Well, now I am going 2 go finde the shift drop for the 450's. Take it easy

[monkeyballs]

Ok here it is for 450's:

final drive Shift drop

2.23 1 3856 1035
1.758 2 4891 1093
1.437 3 5984 1297
1.181 4 7281 1658
0.962 5 8939

[1krazyquadridr]

Sorry I didn't take any pictures. I was advised to use a year 2000 and newer tranny though because they were supposed to be a little bit beefier. In fact, like I stated earlier one of the XR's shafts was bigger in diameter than the EX's so I had to transfer over one of the bearings, everything else looked to be just as strong. I haven't had any trouble with shifting up past third when it has been hot, and I've raced without any problems.

[monkeyballs]

Right on, I am looking foward to doing this. So there must of been quite the noticible diffrence. Do you have any vids? Thanks