Honda ATV Forum banner

1 - 20 of 30 Posts

·
Premium Member
Joined
·
6,522 Posts
Discussion Starter #1
Yesterday I removed ANOTHER 420 motor. This one belongs to a friend of mine's son. It had a rattle in the motor under rev. Not a knock. High pitched rattle.

I recorded it and sent it to shadetree and he said it sounded like a cam chain, and I thought that made sense. It was loudest in reverse, but would do it in neutral too, just not quite as bad. Only does it under throttle.

I took the front case off this morning expecting to find a loose/stretched cam chain or a bad tensioner, but everything was tight and the tensioner couldn't be pushed in (at least by hand).

Any other places to look? I'm going to go ahead and split cases since I have it this far down. Clean it out good. Any areas in the transmission that are problematic on the 420's that could cause a rattle in neutral?
 

·
Registered
Joined
·
1,288 Posts
In neutral it shouldn't be in the transmission. I would lean more towards a clutch issue or something similar.
 
  • Like
Reactions: misterclean59

·
Premium Member
Joined
·
6,522 Posts
Discussion Starter #3
Hmmmmm. What could cause noise in the clutches?

I really, really thought it was going to be the cam chain. If it were wouldn't I be able to see where the chain was rubbing the case though?
 

·
Premium Member
Joined
·
38,518 Posts
just a thought, what about the water pump impellor ?
 

·
Premium Member
Joined
·
38,518 Posts

·
Premium Member
Joined
·
6,522 Posts
Discussion Starter #9
Link pops up for me.


That one work?

The cam decompressor is loose as hell. I THINK They are supposed to be that way, but it's been awhile since I've really inspected one that closely.
 

·
Registered
Joined
·
7,361 Posts
that sounds more valve train related to me.

check to make sure cam bearings haven't failed. loose valve seat, bent push rods, etc. that cam has a decompressor on it, that could also be the source. inspect closely.
 

·
Premium Member
Joined
·
6,522 Posts
Discussion Starter #12

Cam bearings looked good, and the noise seems to be coming from under the front cover, not up in the top end.

How loose should the decompressor be?
 

·
Premium Member
Joined
·
38,518 Posts
https://www.youtube.com/watch?v=jrlWCsLw60Y

Cam bearings looked good, and the noise seems to be coming from under the front cover, not up in the top end.

How loose should the decompressor be?
never gave it much thought on the decompressor ?. it just moves one way. as for the front cover noise ?. have a good look at the clutch basket springs on the big wheel. as well as the springs on the centrifugal clutch arms.
 

·
Premium Member
Joined
·
6,522 Posts
Discussion Starter #14
https://www.youtube.com/watch?v=jrlWCsLw60Y

Cam bearings looked good, and the noise seems to be coming from under the front cover, not up in the top end.

How loose should the decompressor be?
never gave it much thought on the decompressor ?. it just moves one way. as for the front cover noise ?. have a good look at the clutch basket springs on the big wheel. as well as the springs on the centrifugal clutch arms.
Clutch basket springs looked ok. I had to take them off to get the clutch off when tearing it down.

I do need to look at the clutches much more closely.

Have been messing with this thing 25 mins at a time. Yesterday all I did was pull the cam and flywheel, and split the cases and get a quick look at the transmission.
 

·
Premium Member
Joined
·
6,522 Posts
Discussion Starter #16
For comparison the center shift fork.

Might be a slightly bent shift fork?

Wondering if the noise I was hearing is the gear rubbing on the shift fork.

It's getting a new one either way. They're only about 10 bucks
 

Attachments

·
Registered
Joined
·
7,361 Posts
that is definitely going to make some serious noise while running the atv. I'm sure that's the issue because it only makes the noise when driving and that gear is rubbing on the fork when moving.

I wonder if a thrust washer is missing between those gears?
 

·
Premium Member
Joined
·
38,518 Posts
For comparison the center shift fork.

Might be a slightly bent shift fork?

Wondering if the noise I was hearing is the gear rubbing on the shift fork.

It's getting a new one either way. They're only about 10 bucks
wow..lol, that shift fork is gone !. make sure to inspect the shift drum !.
 

·
Premium Member
Joined
·
6,522 Posts
Discussion Starter #19
that is definitely going to make some serious noise while running the atv. I'm sure that's the issue because it only makes the noise when driving and that gear is rubbing on the fork when moving.

I wonder if a thrust washer is missing between those gears?
That was my first thought too, but I checked, and the transmission was exactly the way it shows in the schematic, which makes me think the kid hammered on it and tweaked it enough to make it rub

wow..lol, that shift fork is gone !. make sure to inspect the shift drum !.
Shift drum looks good. I checked it out after finding something very interesting.

If you look at 420 transmission problems, it's almost always 4th gear.

If you look at the 07 420 parts list, 4th gear is $181. If you pull it up on Partzillas site, it shows the gear set AND a new shift drum.

If you pull up just the shift drum for an 07 420, it's just the drum, and it's...wait for it....$181. Different part number than the 4th gear package too.

Anyhow, I'm going to order a shift fork, carefully put this thing back together and make sure everything is exactly right, and then bolt it back together.
 

·
Premium Member
Joined
·
6,522 Posts
Discussion Starter #20
Parts ordered.

Doing new rings with hone
Top end gaskets
Front and rear output seals
Shifter seal
Reverse seal
Timing chain
and of course, the new shift fork.

By the time I figure in a tube of Hondabond, oil, and filter, he'll be a hair under $200.

I'd say he's getting off cheap.

I keep saying I'm done with the charity work, so he's also gonna be buying my beer every time he rides with us for the foreseeable future.
 
1 - 20 of 30 Posts
Top