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Big fan of the LTH 7 plate clutch as an alternative to BGM.  Similar cost, but have yet to have one LTH misbehave at all

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I was having this issue with one I just installed in my Vijai last week. I think I fixed it but I won't know until tonight.

I set my clutch lever free play at about 1mm between the lever and the perch. It's how we always did it at the dealer and as silly as it sounds, I am not really willing to change that. I am always afraid of clutch drag on Lambrettas and going to 3 or 4mm just seems like sloppy work.

What I determined was that when the lever is pulled in, the clutch pressure plate is binding ever so slightly with the crown wheel causing it to drag since it's basically mechanically locking together the clutch. What I did to fix it was put a .4mm shim between the spider and crownwheel so when the pressure plate is down as far as it goes, it leaves just a tiny bit of space between it and the crownwheel. That pushed the end of the spider that runs on the bearing slightly too far into the crownwheel so if I fit it, it would have have bound. Since the inner race on the BGM clutch crownwheel is hardened, filing, lapping, etc was off the table. To get around it, I found an LD engine tab washer that fit perfectly in the gear cluster end shaft and was essentially the same width as end of the spider. I removed the tabs from it, made sure it fit correctly and got it all fit together last night.  I just need to finish closing it up and will test it tonight after work.

Long story and probably confusing without pictures but if people are having this issue, the easy solution would be to add a few mm of free play between the lever and the perch so the pressure plate and crownwheel can't bind together when the lever is pulled all the way in.

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It's great you found a solution. That's a lot of work to make a $400 clutch work that is advertised as plug and play. No disrespect to you, but the manufacturer should be ashamed. 

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Oh I wholeheartedly agree. I knew I would be in for it from your original post but for whatever reason, I decided I would be a masochist and give it a go.

It's funny the Casa Performance team apparently has used these clutches and has nothing but praise for them. Apparently they also must enjoy a little more slop in their lever or are shimming them like I did but not telling anyone. Also a dog leg lever would probably do the same thing so maybe they all use those, but I can't stand them.

I only followed up on this because the internet is scarce on this issue.  Hopefully it steers future buyers to either a solution or a different clutch.

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How does more play in the lever reduce drag in the clutch? Did I miss something? I’d think it would make it worse since you wouldn’t be able to compress the clutch fully. 

 

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The drag isn't really drag (in the normal sense). Using my typical 1-2mm of play at the lever is forcing the pressure plate against the crownwheel and creating the perception of clutch drag. Crazy right?

 

I figured it out when I was using the clutch compressor bolts that come with the kit. The pressure plate and spider should have spun freely inside the crownwheel when they are installed and the springs fully compressed but on the BGM clutch, it doesn't. That would be a lot harder of an issue to chase using a typical clutch compressor since when that is cranked down, it keeps the spider and pressure plate fron turning.

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So, this clutch assembly ended up at my place. We finally got around to installing it today. I totally forgot that it was the "problem" clutch from this thread. Of course, I torqued the clutch nut down...and it locked solid. A quick search brought me back here, so I figured I would follow up. 

The ruler clearance showed about 0.002", which should be ok. After playing around quite a bit I found that the assembly didn't lock up until after 40ft/lbs, so it wasn't much that needed to come off! Fortunately, I have a surface grinder about 10 ft from the engine. It took about 10 mins to grind 0.0015" off the back. It took longer to zero the wheel than to cut it. Re-assembly went fine. I tried the original crown wheel and the clearance was the same. It appears to be an issue with the center spider. When I was reading 0.002" on the original set up, I substituted for another BGM spider and it showed 0.004". 

For this small of an amount I chose to take it off of the back of the sprocket, without checking chain alignment. Taking off where I did, the sprocket will be dropped back an equal amount. If this issue was larger, the correct way would be to check chain alignment first, then find out which side of the sprocket needed machining. It's nice to have a full machine shop in the same place you build engines ?
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I HATE a lot of BGM junk. Really glad you found the answer and posted the solution. It's bs the shop that sold it to me wanted me to send it to them on my dime so they could "check it out". Loop hole jumping. Shops, just back up brand new $400 items...

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On 9/3/2018 at 6:54 PM, Solerunner1 said:

So, this clutch assembly ended up at my place. We finally got around to installing it today. I totally forgot that it was the "problem" clutch from this thread. Of course, I torqued the clutch nut down...and it locked solid. A quick search brought me back here, so I figured I would follow up. 

The ruler clearance showed about 0.002", which should be ok. After playing around quite a bit I found that the assembly didn't lock up until after 40ft/lbs, so it wasn't much that needed to come off! Fortunately, I have a surface grinder about 10 ft from the engine. It took about 10 mins to grind 0.0015" off the back. It took longer to zero the wheel than to cut it. Re-assembly went fine. I tried the original crown wheel and the clearance was the same. It appears to be an issue with the center spider. When I was reading 0.002" on the original set up, I substituted for another BGM spider and it showed 0.004". 

For this small of an amount I chose to take it off of the back of the sprocket, without checking chain alignment. Taking off where I did, the sprocket will be dropped back an equal amount. If this issue was larger, the correct way would be to check chain alignment first, then find out which side of the sprocket needed machining. It's nice to have a full machine shop in the same place you build engines ?
 

Any time I've had clutch drag problems like that I found about .007" cured it nicely. I think it's a little larger than MBD suggests but I haven't had any issues.

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On ‎9‎/‎5‎/‎2018 at 7:08 PM, Mike Anhalt said:

Any time I've had clutch drag problems like that I found about .007" cured it nicely. I think it's a little larger than MBD suggests but I haven't had any issues.

I thought about going further myself. 0.002" can turn into 0.001" under heat. Too much heat can turn it into 0 pretty quick! When you think of it that way, 0.004" isn't really much clearance. Personally, if I didn't have a book to consult I would probably set it around 0.010", which still really isn't that much! I decided to follow sticky's book spec. 

 

On ‎9‎/‎5‎/‎2018 at 6:39 PM, Stu aka S.Hanson #17 said:

I HATE a lot of BGM junk. Really glad you found the answer and posted the solution. It's bs the shop that sold it to me wanted me to send it to them on my dime so they could "check it out". Loop hole jumping. Shops, just back up brand new $400 items...

I totally understand your frustration! You have every right to have a problem with this situation. That said, having sort of been on the "production" end of things (and getting more and more into it!), this sort of thing is a very easy pitfall for a company, especially one that doesn't actually have a factory to make things. They design on a computer, get quotes, and go with their best judgement. Things like hardness (an issue they've had) is almost impossible to measure after the fact, unless they checked every individual part, which they don't. The important thing to me is how they handle a mistake when it happens. 

It's also a simple error that cost you a lot of money and that sucks!

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