Yamaha RX1 Engines

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Posted

I am seriously wondering how long that clutch will hold up.  I could hear the rattle in it when he started to take off in one of the videos on FB.  From my experience, when I heard that rattle it was time to pull it apart and check it out as the front plate or the springs were loose and about to do some damage.  I have a lot of hours on the clutch and have had to pull it down several times.  When you let that rattle go unchecked for too long it will take out the clutch, break towers, snap face plate bolts and have chunks taken out of the clutch material... I tossed my clutch on the last engine swap as I got tired of dealing with it.. and that was on a 582.  Yes I miss it, but I can tell ya straight up that they are not without some worries.

:BC:

 

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Posted

Got a little more done on the RX1 install, got  the cowl fitted on ,had to cut the cowl opening around C drive but im pretty happy I didn't have to do any other mod

Avid Cowl RX1.JPG

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Posted

Looking nice!

Pretty soon it'll be you and Steve Henry out there making us all envious! 

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Posted

 

I am seriously wondering how long that clutch will hold up.  I could hear the rattle in it when he started to take off in one of the videos on FB.  From my experience, when I heard that rattle it was time to pull it apart and check it out as the front plate or the springs were loose and about to do some damage.  I have a lot of hours on the clutch and have had to pull it down several times.  When you let that rattle go unchecked for too long it will take out the clutch, break towers, snap face plate bolts and have chunks taken out of the clutch material... I tossed my clutch on the last engine swap as I got tired of dealing with it.. and that was on a 582.  Yes I miss it, but I can tell ya straight up that they are not without some worries.

:BC:

 

When you say the springs were loose, did they loose some of their elasticity or did the face plate bolting come loose? I heard that the main killer to these clutches is running them up and down at around engagement rpm so they are slipping a light perhaps in a amphip application. I heard if you go past the engage point and don't hangout there a lot heat wont build up and ultimately causing the spring to weaken. I know for a fact Steve started having that noise almost right away after installing the clutch and he called the designer of the clutch noises and he assured Steve that it was nothing to worry about. He questioned Steve on the application and the HP and he said it would be fine at the higher HP because of the high RPM since it will push the weights out even hard into the drum and that the drum is robust enough to handle the extra centrifugal force. But knowledge and experience being king here I am really interested in your specific failure parts and what exactly came loose. At what hour interval did you experience a failure. At what rpm did you run the engine at primarily. Sorry for all the questions I just want to gather as much data as possible a compare to the RX operating conditions and to possibly save Steve Henry from a failure. Thanks

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Posted

First failure was around the 150 or so hour mark... I did use it on floats a lot, but I never dicked around in the engagement RPM area.  I was on it or not.  I have had both the face plate coming loose and rattling around and the spring stretch so engagement was at a much lower RPM.  When the front face plate came loose it snapped 2 of the tiny screws off and they rattled around in the clutch eating up various parts (the ting ting rattle sound he has is what I had going on)  Fixed all that, used red loctite on the screws and it was good to go till the spring got weak.  I still ran it with the weak spring for awhile on wheels and I knew shit was not right as it would sort of engage around 1800 RPM and would be locked up solid and swinging the prop at 2000.  When I changed engines around 400 hrs on the clutch it was toast.  Little face plate screws broke off again, spring broke and ripping up the face of the bell, 1 tower had about 1/2" of the tip of it broke off etc.  I trashed it and went back to the hardy disk.  I loved the clutch.  I really need it for the really cold weather starts etc that I deal with here but I was pissed off at it.  One day soon I will try one again but the first hint of noise coming out of it and I will be tearing it down to see whats going on in there before it destroys itself.  I run the 582 anywhere from 5800 to 6300 continuous. 

I was going to use the clutch on my 800 project, but I didn't think it would last for shit with the increased HP.

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Posted

I think the increased hp is fine as long as you are at a higher rpm to sling the weights out. Thanks for all your info you shared on the clutch.

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Posted (edited)

I'll give actual experience (akflyer) 10 times more validity than engineering estimations , so thanks akflyer for describing your experience with the clutch!  It gives any of us using the clutch fair warning about what can happen... and what to watch for.  That's invaluable info to have!

:BC:

But, I did recently run across the designer of the RK400 (actually the original designer, rights of which were later sold to the current RK400 manufacturer)

Just to get his take on the topic, I emailed him the question below and his answer seems to speak from both engineering estimation and where he has seen the clutch used.

My question: "Would you have an opinion on it's (RK400) use on this (Yamaha Genesis) motor: Output shaft (PTO) rpm range typically 5500 to 7500, max 8000 and 140 HP"

His answer:

The clutch is locked at 2500rpm, and has run on highly modified engines producing over 200hp, and even stock 670cc Rotax make the same hp as your Yammy, but build a lot more torque sooner, so the clutch will last you well over 1000hrs before any wear will even appear, baring any prop strikes, and on mishaps where that has happened, clutch and engine damage is rare.

 

 
Edited by MN Kitfox 2
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Posted (edited)

The above quote from the designer seems to support the idea that the clutch will hold a considerable load as long as it is fully engaged (higher rpm).  

It would be interesting to know more details on the 200+ HP applications.

I can only assume that this guy has many many years of his life wrapped into the design, sale, and follow up with this clutch.  Unless he is overestimating it for some reason, his confidence in it is encouraging. 

Edited by MN Kitfox 2
See my next post below
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Posted

The 670 is no joke, it out pulls the 912 when the 670 is detuned for aircraft use. I can see the 670 out pulling the Yamaha RX1 in a snow mobile race tune. 

 

IMG_1565.thumb.JPG.6450068daeab0b7c74649

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Posted

I'm not sure if this 670 tune is full out race spec?IMG_0109.thumb.JPG.09565479981f8345b1535

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Posted

Here'a a quick google search of the RX1 vs the 670. The 670 HO was legendary. 

*********

All 670s are not created equal. the 99 670 H.O. was the last rotary valve motor that Ski-doo would put in a sled. the zx chassis would not fit the rotary motors. The engineers at doo built that motor as the last hurah for the rotary and pulled out all the stops. Consider that it dynoed at 138 hp, nearly the same as a stock 2002 reed valve 800 doo. The pipe on the H.O. was a seperate part number only for the H.O. The only aftermarket pipes that would make more power were twin pipes. The ignition had a different advance curve. The clutching was nearly perfect out of the box. The standard 670 was nothing like the H.O. Nothing was quicker untill polaris came with the xc 700 and it would still beat that or the 2001 srx in 660'. I owned #243 Toni H. 99 670 H.O. and after that a 2002 mxzx 800.

**************

Yamaha suspension technology, that's funny. I had a 03 rx1 as well ad a 07 nytro. I would take the ride of my 97 mxz670 any day over those. the only thing that the yamaha has for an advantage would be flatter cornering. the rotary valve engines sit high in the chassis because of the intake . yamaha leaves a lot on the table as far as engine and clutching.

i have owned 4 r.v engines that were all bulletproof. 10k+ on two of them. some people are installing them into zx and rev chassis sleds . the ho 670 is a reliably powerfull mill.
polaris introduced their 700, which was quicker than a standard 670. the ho was a response to that engine. it was fast. the 03 firecats which are the fastest are incredibly fast .
the ho actually had quicker drag times.

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Posted

For those that weren't aware the 2016 year 582 Rotax 2 stroke aircraft motor is very close to the same motor as the 1999 model year 670 Rotax minus cylinder bore, rotary valves and the 1 piece crank. The cases are almost identical. The 670 Ski-Doo Rotax is closer to the 582 aircraft Rotax than the discontinued 618 aircraft Rotax was. Some say they discontinued the 618 from the aircraft line beachside it was too similar to the $20,000 912 four stroke Rotax that came market in the same generation. 

It would have been amazing to have had Rotax continue the 2 stroke aviation line with direct injection. It would for sure cannibalize the 912 four stroke line of engines and the current bottom line net income. I don't blame them from a business perspective. 

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Posted

For those that weren't aware the 2016 year 582 Rotax 2 stroke aircraft motor is very close to the same motor as the 1999 model year 670 Rotax minus cylinder bore, rotary valves and the 1 piece crank. The cases are almost identical. The 670 Ski-Doo Rotax is closer to the 582 aircraft Rotax than the discontinued 618 aircraft Rotax was. Some say they discontinued the 618 from the aircraft line beachside it was too similar to the $20,000 912 four stroke Rotax that came market in the same generation. 

It would have been amazing to have had Rotax continue the 2 stroke aviation line with direct injection. It would for sure cannibalize the 912 four stroke line of engines and the current bottom line net income. I don't blame them from a business perspective. 

One thing to keep in mind is yes the 670 may have more horse power but the down side is the RPM to get that advertised HP.  Its not a 2000 TBO engine and no way would I fly my wife and kids behind a 2 cylinder rotax pumping out 130 HP.   The rotax 912 ULS will cannabilize the 670 because the 912 will continue to run long after a 670 needs overhauled.  Your cost to do 300 hour overhauls on a 670 for the life span of a 912 will be $12,006.  That is 6.67 overhauls at 1800 each.  Then add the 670 engine costs new of 5500.  Total cost is $17,506 for a 670 compared to an initial cost of $15000 for a rotax 912 ULS which is far more reliable than a 670 screaming through the air at 7000 rpm to reach 100 HP (my guess on performance at 7000 rpm.).  I have rode with many a guy that have high performance snowmobiles.  Never been on a trip where someone didn't burn down an engine or something periphrial went wrong.  The purpose of the introduction of the 912 was longevity with power to make an affordable engine that is half the cost of a new continental.  Now for the Brave hearts I get the 130 - 140 HP attraction.  I would do it to if I was not flying passengers. For longevity, HP, and power to weight their is no comparing a rotax 912 to a 670.  Remember when your 670 is on the work bench doing an overhaul 6.67 times I will be flying overhead for 2000 hours.  I don't think you can even overhaul a 670 6.67 times.  At some point the entire engine will need changing.  All in good fun.  :-). 

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Posted (edited)

Ok.... A lot of info there.   But, back to this topic, I guess the info above does validate the clutch designer's claim on the 670 HP, which is a good thing.

It means he is not exaggerating, or stretching the facts in that part of his statement, which adds validity to the rest of his statement.

I will edit out my above comment questioning his claim that the power output of the 670 is equivalent to the Yamaha Genesis.

Edited by MN Kitfox 2

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Posted

Steve henry made it back f to idaho from the copperstate flyin. He noticed his clutch drum was rubbing on the gearbox housing so investigated more and noticed one of the rotax ball bearings had failed. The cage was missing and the balls were free to float. It is the lower shaft bearing. We are just hypothesizing right now that maybe the clutch drum causes heavier loads on the in put shaft bearings. He is going to go back together with the stock rubber dampener and no clutch drum. Put hours on it on and inspect the bearing around the 50 hour mark and repeat. 

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Posted

Steve henry made it back f to idaho from the copperstate flyin. He noticed his clutch drum was rubbing on the gear....

Glad Steve made it home OK!

Few thoughts to add into the think tank:

1.  Make sure to check the output shaft bearing on the engine.  If it starts to go bad, the clutch would wobble and vibrate, putting alot of stress on that gearcase bearing.

2. Some people have reported clutches that were out of balance (think they weighed each puck to see if they were the equal).  If a snowmo clutch is out of balance far enough it can take out the engines pto bearing (or in this case a gearbox bearing)

3.  I think steve had a prop harmonic issue a while back with another ratio.  If that was bad enough do you think it could have damaged the gearbox?

Also, If you guys haven't talked to Tony at Twisted Metal Racing, it would well worth your time to add his expertise.  He designed the clutch 20 yrs ago and has been selling it (and the c box) ever since.  He has told me of successful applications over 200 hp, and other applications (commercial airboat) that take a LOT more abuse than in airplanes.

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Posted

Glad he caught before it got serious ,thanks for the heads up.

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Posted

I bit of more information on steves bearing failure. It appears that the thrust shims that are installed on the pinion shaft may have contributed to the bearing failure. Rotax claims that if the shims are not set correctly then premature bearing failure will occur. I have in my instructions to install the shims but some gearboxes dont have the shims just depending on the clearances. I should enphasize to everyone that it is a good idea to check this clearance if you get a used gearbox and everytime the gearbox is assembled. The shims are basically just a thin washer and are available from rotax. Now that steves bearing is bad we cant take that measurement to conclude that this was the cause but its pointing in that direction. On a side note while going through rotax service bullitins i found a that the c gearbox load rating is the same as the 912 gearbox.

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Posted

Update on terrys avid. Header almost done

IMG_7741.jpg

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Posted

Is mine next in line?

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Posted

Is mine next in line?

Put mine in that assembly line too!!

Got my RX1 all tuned up and ready for snow testing yesterday.  Service manual calls for oil filter change every 12,000 miles ( 350 snow hours)!  Mine still had factory filter on it, which will be nice since i can dissect it and see whats been in the "bloodstream".

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Posted

Exhaust is looking good,what type of muffler do you normally use,we were thinking of using a super trap on mine. Good idea  on inspecting the oil filter  :BC:

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Posted

Steve used the Suzuki GTX titanium muffler. 

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