Montesa 4RT Dragging Clutch Advice

[jonnyc21]

The only time I had a problem like Brucey indicated "Selecting gears becomes difficult once the bike is hot and neutral is pretty much impossible to find at any time with the engine running" was when I needed to bleed and re-adjust the levers on my 4RT. 

Best I could tell was that the heat on the slave with the dirty fluid was causing it to not work correctly.  My best guess is because of the age and hygroscopic aspect of the fluid had collected to much water/dirt and was causing issues.  Fixed with adjustment and a double flush of the system. 

I can't say that is the cause here but was in my case.  At least it sure sounds like something in the slave and/or the master to me... 

Best of luck.

[brucey]

19 hours ago, konrad said:

Excellent.  Maybe this is a good place to post the following?

I'm also very fussy and only change one thing at a time because I want to understand the effects rather than just fix a problem.  I'm running 4 clutch springs.  As expected, the force required to pull the lever decreased.  This is a good modification for me as I have a wimpy finger and use the clutch constantly.  Have not noticed any slipping, but when I do it will be time to replace the friction plates (I'll be inclined to use OE or EBC).

My bike is currently running the HTX 740.  That oil has the characteristic gearbox-specific smell which I find most unappealing.  I also think it's an odd choice for the job.  Elf says it's designed for very high performance dry clutch applications like 2-stroke GP bikes and shifter karts.  HTX 740 is a special-order item in the USA, and costs $50 per liter.  I'd like to find a substitute. 

I often use the BITOG website https://www.bobistheoilguy.com/forums/ubbthreads.php to find 40 and 100 degree C viscosity data for various oils.  There I learned that HTX 740 is a synthetic that measures 21.4 centistokes @ 40C and 7 cSt @ 100 C.  Also discovered that Valvoline Dexron-VI synthetic ATF is a possible substitute rated 29.5 cSt @ 40C and 6 cSt @100 C. (Which does not seem all that close to me.)  I bought  the Valvoline locally for $5 per quart, but have yet to try it. 

I have used my own viscosity measuring setup (shown below) to get a feeling for the difference.   I often test suspension fluids by flowing 10cc through a burette at ambient temperature.  My result for used HTX 740 was about 42 seconds @ 57 degrees F, whereas virgin Valvoline Dexron-VI came in at 62 seconds @ 57 degrees F.   Clearly the HTX is considerably less viscous at 57 degrees F, but possibly has sheared down somewhat from virgin.

 

Thanks Konrad. I also noted the Elf oil was very ‘runny’ ??

[coochb]

The clutch actuating fluid replacement is interesting and worth trying

I have just replaced the gearbox oil on my 2017 4RT Standard. From the dealer I bought it from it was probably RockOil Gear Pro.

ELF oil difficult to get in New Zealand though not imposssible. I was going to use RockOil again but special order from local Motorcycle shop. When I explained I wanted a really light oil they suggested Maxima MTL75W which they had in stock.

I changed it this afternoon and so far really impressed with the 30 minutes I tried around the back garden. The clutch feels much more progressive and easy to modulate. Easy to find nuetral as well. The real test will be how it performs when fully hot during a days trials competition but so far so good

Interesting the specs for the Maxima oil are 32cSt@40c and 6cSt@100c, very close to the ELF specs and the added advantage of being intended for use with wet clutches.

[konrad]

I knew nothing about Elf lubricants before seeing it was specified for the Montesa gearbox.  This Wikipedia entry https://en.wikipedia.org/wiki/Elf_Aquitaine says, "From its very beginnings Elf used motor racing as a means of promotion."  Lots of companies do that, but Formula 1 has got to be the most expensive way possible!  Makes me wonder if HRC's specification of HTX 740 might have more to do with a business relationship than being the best fluid for the job?

I changed my gearbox oil to Dexron-VI last night.  Riding in my yard, the clutch seemed less draggy right away (before the fan runs).  But as coochb said, the real test will be how it performs in an actual trials. 

And is it ELF, Elf or elf?  Completely inconsistent usage on their own website.

Edited May 17, 2019 by konrad

[jonnyc21]

This is my own opinion/speculation based on what I have experienced and see... so take it with a grain of sand 

Based on the way my Montesa’s clutch responds to other oils I have used and in comparison to what advanced riders like in a clutch I think the ELF is likely to be used because it actually works... or at least more often then not.  

The other factor to say it isn’t just business from my mind is that they have recommended the ELF from the beginning, even my friends 05 4RT and my 07 as well as my 2017 300RR all recommend the ELF oil.  

I just don’t see that many years of using the same oil really bing just business if it wasn’t good.  People would have complained and they would have changed it at some point.

though I don’t doubt there is more to it than just that... as business relationships are always a part of it.  

Edited May 17, 2019 by jonnyc21

[coochb]

I believe the main reason ELF oil is recomended is that it is an oil which Montesa is confident meets the requirement for a really light gear oil that will make their clutch feel acceptable.

When you get past the oil manufacturers "weight" grading and drill down into the specifications you find huge variations in the cSt, or thickness, values of 75W oils from different companies so Montesa could not just specify " any 75W equvilent" and be confident of the results. Equally they would be hard pressed to list all the diferent oils individually which do meet the requirements so have resorted to simply naming one oil that they know will work.

Unless ELF oil contains magic fairy dust any oil with similar charactistics will perform in a similar manner.

Interestingly this problem also occurs for Fork and shock oil. When you compare the viscosity of different brands of fork oil using a more appropriate method of measurment you find that one brands 5W oil has the same viscosity as another brands 15W oil. 

[jimmyl]

Think the elf oil was spec on the 315r also but as with the 4rr atf works equally as good as designed for very pack clutches with a smooth take up and minimal flare ??

[konrad]

Here's a link to a white paper by the US firm Lubrication Engineers: https://www.lelubricants.com/lit/news/White%20Papers/simple_viscosity.pdf   It's entitled Putting the Simple Back into Viscosity, and I think it adds something to this discussion.

I'm not saying anyone here has this misunderstanding, but it's commonly thought that "W" stands for "weight" when talking about oils.  As the paper points out, '...the grades denoted with the letter “W” are intended for use in applications operating in low-temperature conditions. The “W” was originally coined for lubricants that were considered “winter grade.”  Today, these products are formally called multigrade lubricants, whereas the grades without a “W” are recognized as monograde, or straight grade, lubricants.'

I'll also direct your attention to the viscosity equivalence chart for engine oil and gear oil found on page 6.

[brucey]

Just an update. I carried out the drilling mod and fettled the clutch outer basket. I also lightly filed the fingers on the friction plates. 

I refilled with Elf oil and tried it up and down the road. It was dragging worse than ever?. 

I decided there was nothing to lose by ‘bedding it in’ so I put it in 4th and slipped the clutch for 50yds.  Hey presto! A working clutch??. I can push it easily in 1st with the engine off and clutch in. It starts in gear and I can just about get neutral. 

I just need to see how long it will last. Hopefully a long time?

Thanks for all your advice guys?

[jimmyl]

Glad your sorted but trying to get around the logic of your problem/solution.

If I read your post correctly you had this issue with 2 completely independent sets of friction and steel plates.

Therefore would think the problem is not related to that  -you have done all the mods to the basket etc with no improvement so would think not that.

Slipping the clutch you would think would only have an effect on the clutch plates but we have ruled them out  as you have had 2 sets.

Slipping the clutch so aggressively though could generate a lot of heat which then transferred to slave cylinder or other parts of the actuator mechanism - or maybe some water in the brake fluid which has now boiled off. Maybe a partly sticking piston which with heat has freed off.

May never know??

Hope it stays working fine though for you.

 

 

 

 

 

[konrad]

I now have about 3 hours, over 3 days of riding, on the Dexron-VI.   At first I thought the Dexron-VI was a bit grabbier initially (before the fan runs the first time).  Maybe the friction plates had to get fully saturated with the new fluid?  Now I think that if there is any difference, the HTX 740 may be slightly worse in terms of range of clutch modulation.   They seem to perform very similarly.  To discern any real difference, I think you would have to ride the bike back-to back under exactly the same conditions with two sets of new friction plates that had only been in contact with the fluid to be tested.

[brucey]

On 5/20/2019 at 2:10 PM, jimmyl said:

Glad your sorted but trying to get around the logic of your problem/solution.

If I read your post correctly you had this issue with 2 completely independent sets of friction and steel plates.

Therefore would think the problem is not related to that  -you have done all the mods to the basket etc with no improvement so would think not that.

Slipping the clutch you would think would only have an effect on the clutch plates but we have ruled them out  as you have had 2 sets.

Slipping the clutch so aggressively though could generate a lot of heat which then transferred to slave cylinder or other parts of the actuator mechanism - or maybe some water in the brake fluid which has now boiled off. Maybe a partly sticking piston which with heat has freed off.

May never know??

Hope it stays working fine though for you.

 

 

 

 

 

Jimmy,

I have run the bike for a decent test/practice session and all still seems fine.  I am able to start the bike in gear and even select neutral if I'm careful ?

I think I probably had a number of small issues rather than 1 single cause.  Replacing the fluid, removing all burrs and drilling additional drain holes have all definitely helped.

I didn't lube the used plates when I reassembled the clutch which may be the reason they needed a little 'slipping action' to get some oil between them.

I'm starting to like the bike again!

 

Thanks for all the advice.

 

Bruce.