Clutch slipping at speed, need input! - Honda ATV Forum
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post #1 of 15 (permalink) Old 06-27-2019, 01:19 AM Thread Starter
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Question Clutch slipping at speed, need input!

So I have a new (to me) 1988 TRX300FW. Runs really well, but having some issues. I've tried to google this every way from Sunday, but I'm not getting a definitive answer. I've even seen this exact question asked before, the the replies were vague at best.

So here's my situation. When I first got it, I didn't notice any clutch slippage. But as this is my first ATV, I may not have been noticing. To be honest I took it down the dirt road only once, so that was the only time I had it "up to speed". I did ride it around the woods, and back in a quarry behind my house, but in lower gears and never really "full throttle". Put maybe 5 miles on it?

So I changed the oil to Mobile 1 4T motorcycle oil. Took it out afterwords, and noticed in 5th gear and while going up a hill down the street, the clutch was slipping. I wasn't 100% sure that it wasn't doing it before, but it's pretty noticeable. It will "grab" again after a few seconds, but it was defiantly slipping. If it was doing it before the oil change, it wasn't near as bad. (I think)

The next day I got my new tires in. I went 1" bigger. From 23" on front and 24" on the rear to 24" and 25". Now it's REALLY slipping in 4th and 5th gear when I'm out on the road and going 30-40 ish uphill. I also think I'm noticing it slipping in 2nd gear or higher if I'm not downshifting when I could/should and start accelerating. The taller tires really make more difference than I imagined!

Anyway, I have no idea what oil the PO used, but it was pretty black and likely not lubricating at it's best. Do these clutches not like Synthetic oil? The Mobil 1 is rated for wet clutches, but I'm wondering if the fresh and slicker oil might be exposing worn clutches that the old oil was masking?

Either way, I need new clutches. So is slipping at speed the "shift clutch" or the centrifugal clutch? Can the centrifugal clutch get worn enough to slip like that? Or should it be a non issue since my problems are most noticeable at high RPM and not at low RPM? I'm thinking about just replacing both and being done with it, but I'm no expert. I'd like to hear from some of you that know these bikes better than I do!

I've played with the adjuster, and on mine if I did the counter-clockwise till resistance, then 1/4 turn clockwise, it would "creep" forward at idle and "jump" really bad when shifting into SL. I had to adjust it to about 1/8th. That's about where it was when I started. It does sometimes seem like it's not changing gears as easy as it should. It's not "hard" per say, just doesn't always seem like it's going to the next gear. I sometimes have to give it some gas to get it to "seat" in the next gear. This is only from idle. Shifts fine if I'm moving.

Any input appreciated. Haven't had an "auto-manual" since I was a kid and had a 70cc dirt bike that was "auto-shifting" or whatever the proper term is for these setups without a hand clutch. But I've owned many dirt and street bikes. Thumpers to 4 cylinders. This is just my first quad.

Thanks!

1988 TRX300FW Fourtrax
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post #2 of 15 (permalink) Old 06-27-2019, 06:14 AM
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Doonze, you are looking at all the right things to solve your problem. The correct oil is important for proper change clutch operation. You say your oil is made for wet clutches, so you probably have the correct type of oil. One way to know for sure is that there should be an indication for JASO Standard MA shown somewhere on the back of the oil container. I don't have any direct experience with Mobil 1 4T motorcycle oil. I use Shell Rotella T6 5W40 and don't have clutch slippage problems. My tire size is stock.

Going to larger diameter tires is bad news in my opinion. Others may not share my opinion, but larger tires will increase the load on your clutches and lead to slippage. My advice is to stick with stock tire sizes. You can look forward to continuing clutch slippage problems with larger tires, and will lose some low end torque as well.

You also ask a good question about how do you know if the slippage is coming from the centrifugal clutch or the change clutch. It could be either one. I'm not sure how to identify which is the culprit, but you should keep investigating both until you have it figured out.

2015 TRX500 Foreman
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post #3 of 15 (permalink) Old 06-27-2019, 06:29 AM
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Here is another thing to check on. You say your machine came with 23 inch tires on the front and 24 on the back. If I am not mistaken, in stock form, it has the same diameter tires on front and back. Different tire size front-to-back on a 4WD machine is a no-no because it stresses the drive and causes the tires and/or clutches to slip. The first step here is to find out what the stock tire size is.
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post #4 of 15 (permalink) Old 06-27-2019, 09:55 PM Thread Starter
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Quote:
Originally Posted by ktriebol View Post
Doonze, you are looking at all the right things to solve your problem. The correct oil is important for proper change clutch operation. You say your oil is made for wet clutches, so you probably have the correct type of oil. One way to know for sure is that there should be an indication for JASO Standard MA shown somewhere on the back of the oil container. I don't have any direct experience with Mobil 1 4T motorcycle oil. I use Shell Rotella T6 5W40 and don't have clutch slippage problems. My tire size is stock.

Going to larger diameter tires is bad news in my opinion. Others may not share my opinion, but larger tires will increase the load on your clutches and lead to slippage. My advice is to stick with stock tire sizes. You can look forward to continuing clutch slippage problems with larger tires, and will lose some low end torque as well.

You also ask a good question about how do you know if the slippage is coming from the centrifugal clutch or the change clutch. It could be either one. I'm not sure how to identify which is the culprit, but you should keep investigating both until you have it figured out.
As for tires, I honestly was just trying to get some more clearance. These 300's are low slung to be honest. Before I had 7.25" from the ground to the skid plate. I got more clearance than I thought I would, 9.75" with the new tires to the skid plate. However you are 100% correct. I lost a lot of power on the low end, and it made the clutch SO much worse. If I had it to do all over again, I'd have stuck with the stock size. But I will admit the extra clearance was noticeable out climbing on the rocks. Before I scraped all the time, with the new tires I didn't scrape once. I'll see where I'm at after replacing the clutch. I doubt I'll get new tires before these wear out. And as they are Kenda Bear Claws that might be awhile.

I also think I'll just replace both clutches. Might as well while I'm in there.

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Originally Posted by ktriebol View Post
Here is another thing to check on. You say your machine came with 23 inch tires on the front and 24 on the back. If I am not mistaken, in stock form, it has the same diameter tires on front and back. Different tire size front-to-back on a 4WD machine is a no-no because it stresses the drive and causes the tires and/or clutches to slip. The first step here is to find out what the stock tire size is.
I thought the same thing, but both the manual and Google have confirmed there is a 1" difference front/back. From what I've read, that offset is why these (and a number of other ATV's that also have a offset front/back) have transfer cases. I guess bikes that have 4 tires all the same size don't need transfer cases and just have direct shafts. At least on full time 4x4 rigs. On the TRX300FW the transfer case is geared to compensate for the difference.

Stock is 23x8x11 on the fronts and 24x9x11 on the rear. I haven't found any good info on WHY they offset these, no reason I can image justifies the extra cost to compensate. Some engineer somewhere had some reason I suppose. I've seen a list of some of the others that do as well. Just about everyone had one model that's 4x4 and offset sizes. I'd really like to know their thinking on that.

1988 TRX300FW Fourtrax
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post #5 of 15 (permalink) Old 06-28-2019, 04:44 AM
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@doonze have you tried adjusting your change clutch? There is no certain way to tell which clutch is shifting, but you'll want to check the adjuster screw on the change clutch and make sure that isn't your issue.

Going up 1" in tires isn't an issue when all is good. But when you are noticing a slipping clutch, that means something is right on the verge. So going up in tire size becomes much more noticeable then.

Also, you might want to change your oil one more time. We had a TRX90 we revived a few years back. When we got it from prior owner the oil was very dark. Put T6 in it right away. After getting it running we noticed a clutch slipping some. Changed the oil soon after and it came out very dark again even though it was fresh. There was just that much crap built up inside we think. 2nd round of fresh T6 though and the oil stayed cleaner and clutch stopped slipping.
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2004 TRX400FA (Rancher 400AT)
MotionPro twist throttle kit
12" handlebar mounted light bar
rear rack wheelchair carrier
Cycle Country 48" plow w/ KFI hybrid mount
Champion 3000 lb winch w/ synthetic rope
23" Titan 489's all around (saving clutch)

2011 Grizzly 450 EPS

Others in the family: '04 TRX250TE, '85 TRX250 Utility (X2), '05 TRX90, '06 TRX500FA, '95 TRX400FW,' 88 TRX125
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post #6 of 15 (permalink) Old 06-28-2019, 08:37 AM
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Doonze, good job on checking the stock tire size. Since it was designed to have smaller tires in the front than in the back, then Honda must have designed the drive system to compensate accordingly.

2015 TRX500 Foreman
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post #7 of 15 (permalink) Old 06-28-2019, 09:36 AM
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Quote:
Originally Posted by ktriebol View Post
Doonze, good job on checking the stock tire size. Since it was designed to have smaller tires in the front than in the back, then Honda must have designed the drive system to compensate accordingly.
Yep even as late as the 2000 TRX300FW Honda was putting 1" smaller tires on the front. Even with it designed to have the 1" different diameter, tons of guys here have put same diameter tires front and rear on their 300FW's and they do just fine with those as well. There is enough "give" in the entire system and especially on dirt for it to be ok.
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2004 TRX400FA (Rancher 400AT)
MotionPro twist throttle kit
12" handlebar mounted light bar
rear rack wheelchair carrier
Cycle Country 48" plow w/ KFI hybrid mount
Champion 3000 lb winch w/ synthetic rope
23" Titan 489's all around (saving clutch)

2011 Grizzly 450 EPS

Others in the family: '04 TRX250TE, '85 TRX250 Utility (X2), '05 TRX90, '06 TRX500FA, '95 TRX400FW,' 88 TRX125
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post #8 of 15 (permalink) Old 06-28-2019, 12:41 PM Thread Starter
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Quote:
Originally Posted by wheelsquad View Post
@doonze have you tried adjusting your change clutch? There is no certain way to tell which clutch is shifting, but you'll want to check the adjuster screw on the change clutch and make sure that isn't your issue.

Going up 1" in tires isn't an issue when all is good. But when you are noticing a slipping clutch, that means something is right on the verge. So going up in tire size becomes much more noticeable then.

Also, you might want to change your oil one more time. We had a TRX90 we revived a few years back. When we got it from prior owner the oil was very dark. Put T6 in it right away. After getting it running we noticed a clutch slipping some. Changed the oil soon after and it came out very dark again even though it was fresh. There was just that much crap built up inside we think. 2nd round of fresh T6 though and the oil stayed cleaner and clutch stopped slipping.
Yeah, I played with the adjuster. If I set it like the manual says, it would creep at idle, and jump hard when shifted. So 1/4th turn didn't work for me. I set it at 1/8th a turn and that works great. That also happens to be about where it was set before I messed with it. I also did the "hold the shifter up and give it gas" test, and it didn't move at all. So I think adjustment wise it's spot on.

I've also read others not having issues going up a few inches. Like you said, I really feel it shined a light on an existing problem, but didn't create it. Personally I like the extra clearance. But I have no need to go any bigger. Anything bigger would have to much negative effect on the gearing and low end torque. Only way I'd go bigger is if I did a gear reduction. But I don't have a strong enough use case to justify that!

It's off in Colorado with my Boss this week, but once it's back I'm going to just order up two new clutches and be done with it for the next 10 years! (Or I hope more!) So I'll change the oil again then.

Quote:
Originally Posted by ktriebol View Post
Doonze, good job on checking the stock tire size. Since it was designed to have smaller tires in the front than in the back, then Honda must have designed the drive system to compensate accordingly.
Yes, but it bugs me WHY! Best guess currently in my group of gear heads is that smaller tires turn easier and do better steering in mud. But who knows.

Quote:
Originally Posted by wheelsquad View Post
Quote:
Originally Posted by ktriebol View Post
Doonze, good job on checking the stock tire size. Since it was designed to have smaller tires in the front than in the back, then Honda must have designed the drive system to compensate accordingly.
Yep even as late as the 2000 TRX300FW Honda was putting 1" smaller tires on the front. Even with it designed to have the 1" different diameter, tons of guys here have put same diameter tires front and rear on their 300FW's and they do just fine with those as well. There is enough "give" in the entire system and especially on dirt for it to be ok.
I had read that, and if I'd been unable to keep the 1" offset with the tires I wanted I likely would have as well. But while it "works" and I've heard no reports of people having any major failure due to using 4 matched tires, I can't help but think it adds extra wear. Also my driveway is about 1/4 mile and concrete, and I do ride some amount on paved surfaces. So I decided to just keep the stock ratio. And until someone can explain to me WHY they offset them, I feel it's safer to just keep to what they designed it for. With regards to the offset at least. I already went off the reservation by going 1" bigger all around.

1988 TRX300FW Fourtrax
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post #9 of 15 (permalink) Old 07-01-2019, 01:58 AM Thread Starter
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So I just bit the bullet and ordered a full clutch rebuild kit (plates/disk/springs), a new centrifugal clutch, and one way bearing. While my shotgun approach won't answer my question of which one is to blame, after 31 years I'm certain it could use all new parts. And I'm a big fan of the "while you're in there" approach of automotive maintenance. If I do this right, it should be a long, long time before I have to have that cover off again. (I'll also check my timing chain/tensioner just to be sure).

I'll try to spec what I pull out, and see if anything screams "guilty" on my clutch slippage. If nothing just jumps up and down as the culprit, I'll still post back with my results. I don't think I'll get the parts in till after the 4th of July holiday, so I won't get to it for about 10 days, but I will post my results for others who search and find this thread.

Thanks for the input guys!
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1988 TRX300FW Fourtrax
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post #10 of 15 (permalink) Old 07-05-2019, 03:03 PM Thread Starter
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So all my parts are in, clutches are soaking in motorcycle oil, and I'm just waiting for the bike to return from it's trip to Colorado with my boss. I guess his 16 year old daughter has been riding it, and she's small. So the clutch has been behaving pretty well. I took him for a ride before he left with it, and with both of us on it, it slipped fairly bad going up hills.

Anyway, I've been googling for about and hour, and haven't got an answer to my last remaining question yet. Do I need to soak the centrifugal clutch? It seems to me it also has to be a wet clutch? I suppose it would be self evident once I get it apart, but just wondering since I have a nice oil bath already setup.

Yes, I know the oil soak isn't required per say. As many install them just coated. But as the service manual suggest soaking them overnight, I did the thing. And as they bubble, I imagine it's not a bad idea. Mine will get about 5-6 days of soak. Just wondering about the shoes on the centrifugal clutch, never seen anyone mention it, so I'm supposing it doesn't matter. Just looking to see if anyone has an opinion.

Thanks!

1988 TRX300FW Fourtrax
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