400ex transmission problems - Honda TRX Forum
 
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post #1 of 10 Old 04-06-2019, 12:51 AM Thread Starter
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400ex transmission problems

Greetings, my name is Aaron I'm an electrician. I own a 2000 400ex. I use this site alot to answer alot of my questions that i have when I was rebuilding my 400ex. I ran into an issue and couldn't quite find the answers to my question via other forums/posts. So I decided i would join this forum in Hope's to get information and share some of my knowledge and experience. I am mechanically inclined, I have rebuilt alot of things from motorcycles, quads, small engines ect. However I have ran into a problem with my rebuild on my 400ex. I just put in new weisco crank, main bearings, piston 85mm 10:1, cylinder. New stage 1 cam, rocker arms, valves/springs/seals. When I split the case the tranny gears fell out and came apart. I used a diagram and double checked it 2 or 3 times. When I put it all back together and was going through my break in period I noticed the shifter lever has alot of play in it and it would not let me shift into 3rd. And once in 2nd it wouldn't let me shift back into 1st. I can go through all gears when it's off and I rock the quad back and forth letting in and out clutch but it still is far from smooth.
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post #2 of 10 Old 04-06-2019, 03:49 AM
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This is a tough call without hands on, but I'll do my best to try to help you.

If the transmission shifts with the engine off - there is probably nothing wrong with it.

I gather from your description you are trying to shift through the gears with the engine running, but the quad is stationary? Not being able to shift that way is normal.

The play in the shift lever - may or may not be normal - would need a hands on examination to make that determination.

Please do not extol the modifications or performance improvements when asking about the transmission - you may be excited about what you have done, but it has no bearing on the problem you are inquiring about.

You say "I can go through all gears when it's off and I rock the quad back and forth letting in and out clutch but it still is far from smooth." When it's off what? And the operation of the clutch has nothing to do with the operation of the transmission. The clutch simply disconnects the engine from the transmission.

Let's just tackle one problem at a time - we are addressing the transmission now - if there is a problem with the clutch, we will address it later.

Last edited by Here 2 help; 04-06-2019 at 01:26 PM.
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post #3 of 10 Old 04-06-2019, 01:11 PM Thread Starter
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When I took it for its first ride. Meaning engine is running and I am moving. It went into first gear great. I then let off the clutch and it took off as normal. Went to pull in clutch and put it into 2nd and it was harder than usual. I finally got it into 2nd then after gaining more speed I tried to go into 3rd. It took me 2 or 3 runs to get it actually engaged into 3rd. When I shift up into 2nd or evan 3rd it does not want to down shift. Meaning if in 3rd it does not want to go back to 2nd. If in 2nd it does not want to go back in 1st.
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post #4 of 10 Old 04-06-2019, 01:38 PM
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OK - the transmission is designed to be shifted with or without using the clutch - when the engine speed matches the vehicle speed there is no pressure on the moving parts and it should shift easily.

However, you description of 'play' in the shift lever is probably the root cause of the problem. Does the shift lever move up and down any distance without spring pressure returning it to center? there should be no free play in the shift mechanism - a spring holds it between 'up' and 'down' and there should be pressure immediately upon trying to move it. At rest, gravity will settle it on the 'down' side so the initial movement will be in an upward direction. There should be spring pressure holding it in position and there should be no free play.
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post #5 of 10 Old 04-06-2019, 02:41 PM Thread Starter
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There is about 1.5" of free play (up and down) when in nuetral.
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post #6 of 10 Old 04-06-2019, 02:44 PM Thread Starter
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You have to pull up on it about 1.5" until you feel it wanting to engage the shift. When you let it go it falls to the bottom. It doesn't appear that it has a spring holding it in the center.
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post #7 of 10 Old 04-06-2019, 04:34 PM
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I'll guess the centering spring is out of place or missing or the centering pin is missing

Unfortunately, it requires complete engine disassembly to repair the shift mechanism
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post #8 of 10 Old 04-06-2019, 05:44 PM Thread Starter
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Yea that's what I was afraid of. I just wanted to make sure I wasn't missing anything stupid..... well time to get to work and start disassembling it a 2nd time. Thanks for the info.
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post #9 of 10 Old 04-07-2019, 01:50 PM
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Although all the gaskets are new, do not reuse the gasket between the crankcase halves or the head gasket - I personally will not reuse the cylinder base gasket - the other gaskets can be reused (if you want to) because they are rather easy to change down the road.

Tip from the pro: when the crankcase is together and the shift drum lock is installed; snap a vice grip lightly onto the counter shaft (where the engine sprocket rides), put the shift lever on the shaft (any position is fine and it does not need to be tightened (unless it is worn and slips)), turn the input shaft (where the clutch mounts) with your fingers (or put the inner clutch hub on the shaft for greater leverage) - while turning the input shaft, operate the shift lever - each operation should result in the selection of the desired gear - Note, the gear may not engage fully upon operation of the shift lever, just continue to turn the input shaft - when the engagement dogs line up, the transmission will click into gear - shift through all the gears once or twice to verify proper operation - if there is a problem, it's easier to attack at this point instead of when the engine is completely together and running.

Also note: most people do not shift constant mesh transmissions properly. Most people are familiar with synchromesh transmissions used in automotive products. In the synchromesh transmission, the engagement of the gears is facilitated by a pair of sychro gears that fit inside the power transmitting gears - the two 'sychro' gears are used to spin the chosen gear to the same speed as the drive line so the gears will align and engage - the common sequence of shifting is; disengage clutch, operate shift lever and engage clutch. For constant mesh transmissions that sequence is WRONG! - it may get the job done, but it can result in transmission damage. The proper method of shifting is to disengage the clutch, operate the shift lever (either up or down) and hold it, engage the clutch and then let off the shift lever. Under racing conditions, the clutch is used to modulate the power to the drive wheels and shifting may be accomplished without the use of the clutch - the engine speed is simply increased or decreased to remove driving force from the transmission shafts and the shift is initiated - once again, the shift lever is held in the direction of the shift until the driving force is reapplied - holding the shift lever assures the gears engage when the driving force is applied - if the engagement dogs do not engage fully before power is applied, the engagement dogs may simply skip over each other (missed shift) or may engage violently - both occurrences may result in gear damage.

Let me know how it goes and what you find the problem to be.
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post #10 of 10 Old 04-13-2019, 03:37 PM
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Have you got the problem figured out yet? I just started working on a 400EX and you can see the shift centering spring and pin with just the clutch cover removed. I took a pic of what its supposed to look like. What you cant see is the spring that lifts the pawl into the drum. I'll try to get a video of that working.
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