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Old 09-26-2012, 08:44 AM   #1
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Default Mugen MRX4-X clutch question

I've been out of off road for a few years and vaugely remember my mtx4r centax clutch set-up.

I just picked up a cherry MRX-4X. I know it's not the latest model, but I'm absolutely thrilled to have it in my collection, and hope to find a place to hone my skills before upgrading to new gen.

All that said, I need some help on the most basic of questions. I set the clutch the way I remember. approx .7mm on the clutch spring nut, and I shimmed it with just a little play on the bell.

When I started the car, it wouldn't move with the engine starting. Obviously too much space between the clutch and the bell. I went in an played with shimms some more and got the same thing.

Finally I added enough shims so the bell actually dragged a little on the clutch. The tires finally moved and the car sprang to life. The only problem I have is the car creeps forward even at idle, which tells me the clutch is engaging.

Here is my question. Should I go tighter on the spring nut to .8mm or 1.0mm, or keep playing with the shim?

Hope I didn't confuse...any help anyone can give would be awesome!
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Old 09-26-2012, 12:22 PM   #2
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Pre-Load your spring about 1mm down with the screw.

Shim the clutch so there is a gap of 0.7mm.

You measure this with the bearings on the clutch shoe side removed from the bell.

:-)

Check the manual dude also it explains it better than me.
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Old 09-26-2012, 01:13 PM   #3
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Quote:
Originally Posted by JamesHealey View Post
Pre-Load your spring about 1mm down with the screw.

Shim the clutch so there is a gap of 0.7mm.

You measure this with the bearings on the clutch shoe side removed from the bell.

:-)

Check the manual dude also it explains it better than me.
Thank you. You explained it perfectly.
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Old 09-26-2012, 02:08 PM   #4
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Search on Youtube to: SALVEN CENTAX

Is a good vid with all the explenation.
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Old 09-27-2012, 12:17 PM   #5
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Originally Posted by Roelof View Post
Search on Youtube to: SALVEN CENTAX

Is a good vid with all the explenation.
Thanks for the suggesting I will do that. I think I am confusing myself. I've done exactly what the manual says:

tighten the retaining nut approx 0.6mm to 1.0mm (just under two threads showing above the nut). mine is 0.8mm

ship the clutch bell so there is between 0.3mm to 0.5mm gap between clutch and the bell. Mine is 0.35mm

I heat the engine to operating temp (still very tight), start the engine and gap the throttle but still no wheel spin with wheels off the ground until I hit mucher higher RPM than I feel is safe for the engine under no load.

Mugen tech support said that i need to tighten the retaining nut more to press the 3 shoes closer to the flywheel for a better engagments (lower RPM), but I took it down to 1.5mm (almost three threads showing above the nut) and did not see any change.

Conversely, I started going the other way to where the retaining nut was almost flush with the threads, approx. 0.1 or 0.2 mm and the wheels spin better, but I don't think its anywhere near to race tuned.

I've left the cluch shims alone for now since they are very close the smallest recommended gap, but I am at a loss considering how far off I am on the retaining nut setting.

Any help or advice would be greatly appreciated.
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Old 09-27-2012, 12:33 PM   #6
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the less the spring is preloaded the earlier the clutch engages (LOWER RPM)
more preload Later (higher rpm) you also have to remember that it will take a little time for the shoe to come up to temp and work right my xray for almost the first half minute or better after first start before it will bite at all to even warm and it will take a couple of warm up laps befor it works correctly
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Old 09-27-2012, 12:48 PM   #7
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Originally Posted by azeroth View Post
the less the spring is preloaded the earlier the clutch engages (LOWER RPM)
more preload Later (higher rpm) you also have to remember that it will take a little time for the shoe to come up to temp and work right my xray for almost the first half minute or better after first start before it will bite at all to even warm and it will take a couple of warm up laps befor it works correctly


Thanks dude. Hadn't thought about waiting for the clutch to warm up.

That centax video that Roelof suggested is the cat's A$$, but for some reason my computer goes funky right at the clutch bell gap shim part. Minute 5:36 in the video.

I smell a consperiacy.

Whoever is behind this, please know I am a newbee to 1/8scale on road, I'm a decent wheel, but no need to sabatoge me a this point. Please relase my computer from your evil grasp...
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Old 09-27-2012, 01:09 PM   #8
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OK...

- remove all shims located between the inner bearing and the flyheel nut.
- If you do mout the clutchbell you should be able to push it against the clutch shoe.
- Take a caliper and messure the distance from the top screw to the edge of the 1st pinion.
- Note the value or if you have a digital caliper set the distance to zero.
- pull the clutchbell as hard from the shoe and messure in that position the same distance.
- with a normal caliper you have to calculate the difference and with a digital one you will see directly the difference.
- what you have messured is the gap. That must be 0.7mm so shim it out with shims on top of the thrust bearing so the total play from the clutch shoe is 0.7mm
- from there you have to place shims between the inner bearing and the flywheel nut to get a minimum of endplay.

With this setting and about 1mm on the spring nut your clutch should work fine
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Old 09-27-2012, 01:51 PM   #9
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Quote:
Originally Posted by Roelof View Post
OK...

- remove all shims located between the inner bearing and the flyheel nut.
- If you do mout the clutchbell you should be able to push it against the clutch shoe.
- Take a caliper and messure the distance from the top screw to the edge of the 1st pinion.
- Note the value or if you have a digital caliper set the distance to zero.
- pull the clutchbell as hard from the shoe and messure in that position the same distance.
- with a normal caliper you have to calculate the difference and with a digital one you will see directly the difference.
- what you have messured is the gap. That must be 0.7mm so shim it out with shims on top of the thrust bearing so the total play from the clutch shoe is 0.7mm
- from there you have to place shims between the inner bearing and the flywheel nut to get a minimum of endplay.

With this setting and about 1mm on the spring nut your clutch should work fine

Noted and done all of that, which is why I am confused.

That video did point out somehting that I may have overlooked as it was not mentioned in the manual--before the video cut off, I heard him say "no bearings installed in the bell."

All measurements I've done thus far have been with clutch bearing installed. I assumed that gap is gap and clutch bearings in, actually give you a better measurement since that's how you run the car, but I may be totally off.
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Old 09-27-2012, 03:42 PM   #10
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check gap with inner bearing removed so the bell (bearing) does not give false measurement for gap by the bearing bottoming on hub nut
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Old 09-28-2012, 03:05 AM   #11
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With the Mugen clutch normally there is no need to remove the inner bearing, you chould be able to push the clutchbell on the shoe (check it while turning arround, you should feel the force of the shoe).
With this the clutchbell will stay straight makes it easier to messure the gap.

I have a gapmeter like the one in this tool but just only the gapmeter. It works much easier than a caliper.
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Old 09-30-2012, 08:30 PM   #12
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Quote:
Originally Posted by Roelof View Post
With the Mugen clutch normally there is no need to remove the inner bearing, you chould be able to push the clutchbell on the shoe (check it while turning arround, you should feel the force of the shoe).
With this the clutchbell will stay straight makes it easier to messure the gap.

I have a gapmeter like the one in this tool but just only the gapmeter. It works much easier than a caliper.


Took all the advise everyone gave, and got that clutch working very well.

Thank you to all.
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Old 09-30-2012, 08:35 PM   #13
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Default 1st gear one-way bearing

FYI...after fine tuning my clutch for a few days and countless measuring and finally getting it perfect, I realized, the 1st gear bearing may have been part of my problem-- it was either starting to fail or grease had worked its way in there....

It did not dawn on me until, the car hesitated on a launch after the clutch worked brilliantly.

Actually did it again a few minutes later after a slow turn into a corner with a hard launch exiting.

the 1:8 scale cars are much heaver than my 1:10, so it makes sense the 1st gear bearing takes some hard abuse.

Comments welcome, or am I all wrong?
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Old 10-01-2012, 02:09 AM   #14
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Indeed they do fail from time to time. It is wise when you change the bearing inspect the adapter shaft as wel and change it with the bearing. A new bearing on a worn shaft can quickly cause problems again.
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Old 10-01-2012, 03:37 AM   #15
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Quote:
Originally Posted by luvtorun View Post
FYI...after fine tuning my clutch for a few days and countless measuring and finally getting it perfect, I realized, the 1st gear bearing may have been part of my problem-- it was either starting to fail or grease had worked its way in there....

It did not dawn on me until, the car hesitated on a launch after the clutch worked brilliantly.

Actually did it again a few minutes later after a slow turn into a corner with a hard launch exiting.

the 1:8 scale cars are much heaver than my 1:10, so it makes sense the 1st gear bearing takes some hard abuse.

Comments welcome, or am I all wrong?
the one way bearing is a major component of most nitro on road cars and should be treated as such clean it and oil with one way lube but do not use too much normaly one drop is enough [i use serpent one way lube ]..
mugen now make a one way grease i have not tried it yet so can not comment ..
regular inspection of the whole driveline cluch shoe .gear box , bearings,pinions ,spurs ,belts, and pulleys do this and you will still be racing when others will be droping out thru failures.. At a recent champs i replaced these items after a hard days racing and the car ran like clockwork and i keep the old stuff for club days when it does not matter so much .. just remember 1/8 on road is the F1 of rc and demand regular car work or you will not always finish..welcome to 1/8 scale have fun .. cavey..
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