New 83 YT175 owner needs clutch info from the experts

[dgm635csi]

Hello all,

Ive been a lurker on this site for a few months, and figured its about time I posted a thread.

I recently purchased a 1983 yt175 as a putt-around trike to ride alongside my kids, since my big nasty dirtbikes aren't really fun to ride a lower speeds. I purchased my low hour YT for a low price, and have been ironing out the bugs since I bought it about a month ago. The original owners, or an unskilled shop had installed the pull starter in such a way that it was turning the engine backwards. This made the trike very hard to start, and most likely caused the trike to be set aside in storage for many years. It took me a good week to figure out why it was ripping the pull cord out of my hands, backfiring etc. but after figuring that out, everything else I've needed to do has been pretty minor.

Last week I went on a ride with my son, and discovered that the clutch seemed to slip after its initial engagement. This happens in 2nd gear or higher when applying moderate to heavy throttle. All previous rides had been in the snow, so I didn't notice the slippage prior to last week. The first thing I did was check the adjustment on the pressure plate which turned out to be fine. I had already put fresh oil in the tranny (Amsoil 10w40 motorcycle oil), so I didn't suspect that. I proceeded to disassemble the clutch. The original frictions were moderately worn. The original steels didn't seem to have any wear other than some polishing on the rounded side, and everything else inside the clutch was in good condition including the extra aluminum spacer ring Yamaha put in the 83' clutch pack. There were 8 large ball bearings behind the thrust plate (question about these shortly). The compression springs on the pressure plate measured about .585-.595"

So, I ordered an EBC friction disk kit, and proceeded to install it. After I was finished, I went for a test ride, and guess what? The clutch was still slipping!!

So the trike is torn apart again, and I realized that I made a few errors along the way regarding my installation:

1: I did not scuff up the clutch steels as most people recommend. They are scuffed now, 220grit wet sanded with wd-40 on a glass plate. My service manual does not mention this procedure.
2: I did not install all of the steels in the same direction. The service manual only vaguely mentions the last steel plate being installed with the machined surface towards the inside. None of my steel plates are more than .600". They are not worn.
3: I reused the same pressure plate springs as they are close to the free length specified in the manual (.600), but there is no tolerance listed on this figure so I'm not sure what length is considered to be to short to reuse.

I did install the clutch friction disks, steels, and spacer ring in the correct order the first time when I did the clutch.

Before I put this thing back together again correctly, I've got a few questions for any YT experts out there:

1: There were only 8 ball bearing thrust balls installed on my yt175, but the microfiche shows 10 balls on the 83 model, as well as the extra aluminum spacer disk. Could somebody confirm how may thrust balls an 83' yt175 is supposed to have. The microfiche shows only 8 balls on the 82"model. I don't want to put it back together yet if there are supposed to be 10 balls.

2: Are there any aftermarket options for clutch springs? Yamaha springs are NLA, and I have only been able to purchase 4 off ebay so far. KG offers springs with a full set of friction disks as a kit but not separately.

3: Should the steels be installed in any particular order regarding their thickness? ie: thickest to thinnest?

I really appreciate any info you guys can provide, and look forward to contributing to the forum.

Duncan

[dgm635csi]

Update:

I received 4 NOS oem pressure plate springs, and the measured free length is about .620-.625". So the old springs are about .040 shorter in length. Doesn't really sound like a lot, but its about 7%, so that may make a noticeable difference to have new springs in the pressure plate assembly. I've got a full set of Vesrah springs on the way, so I'll see how those compare to the NOS oem, and original springs.

I still would like to know for sure how many thrust balls are supposed to be installed in the 83' clutch. Someone on this forum must have had there 83' yt175 clutch apart.

Duncan

[dgm635csi]

Update:

I received the vesrah pressure plate springs today. Their free length measures out to be about .675-.857" , almost .100" longer than the old original springs, and about .050" longer than the NOS oem springs. They are also significantly stiffer than the NOS oem springs, so they should stiffen up the pressure plate assembly quite a bit. The vesrah part number is sk-203 ordered through hyperparts.com for $9.13 + shipping.

Since nobody has replied with information regarding the number of thrust balls, I will probably reassemble everything with the 8 balls I have and see how that works before ordering more balls.

Duncan

[dgm635csi]

Final update on this thread:

Success!! After reassembly and testing, the clutch is not slipping anymore.

When I first disassembled the clutch, I found that there were 2 small washers installed underneath each of the four "off" springs mounted to the thrust plate. The "off" springs provide some pressure back towards the thrust plate, which rests against the 8 thrust balls. When your rpm's drop, these springs decompress the clutch pack, and move the thrust balls back into their grooves allowing the clutch to slip at lower rpm's so the engine doesn't stall. I could find no record of these washers in the parts fiche, or in my service manual. My thrust plate "off" springs already measure about .250 longer than the minimum service length in my manual, so I took a gamble and removed the washers. The washers were providing an extra .060 of compression on each of the off springs. so by removing the washers, I reduced the amount of pressure that resists the movement of the thrust balls. This should allow more pressure to be applied to the clutch pack by the thrust plate. There was also the chance that the "off" springs would no longer provide enough resistance to the thrust balls at low rpm, and the engine would stall when placed in gear.

I assembled the clutch pack inside the thrust plate assembly, and made sure to position all of the steels with the sharp machined surface facing towards the inside of the engine, away from the pressure plate.

I used the vesrah springs in the pressure plate assembly. They made it much more difficult to reassemble the pressure plate since they are much stiffer than oem. I actually had to place the entire assembly in my vise to (carefully) compress it enough to put the 4 retaining e-clips back on. I could no longer do it by hand. They also made it much more difficult to get the large clutch retaining clip over the pressure plate and seated into the grooves on the clutch basket fingers.

After final assembly, the end results are excellent. The bike did not stall when put into gear at idle, so removing the washers from underneath the thrust plate "off" springs was not detrimental. The clutch engages more positively than before at a slightly lower rpm. No slippage through all 5 gears on pavement at full throttle!! Now I really know how fast this little trike can accelerate. Pretty impressive power. I should be able to reliably kick the rear end out in dirt now.

Duncan

Duncan

[fishertricar]

Thank you so much for sharing that info, I may use hd cluth springs as I have a yt125 but im going to use a dt175 ported cylinder, some say that at one point of tuning I will be needing to convert to manual clutch but I would like to keep the original semiauto

[fishertricar]

Can you please tell us where did you buy the ebc friction discs? cant find anywhere o the web, only nos oem on ebay and people ask too much for only one disc

[350for350]

Yes when you add more power, you should at least use new clutch springs, if not heavier duty springs. They are basically what transfers your engine's power to the transmission and rear wheels. If they don't hold strongly enough, then the engine will overpower the springs causing the clutch to slip. That may not the best way to explain it, but it's the only way I know how to.