Low RPM @ takeoff, runs fine at speed

25 posts in this topic

Posted

So have a new behavior that is not all that bad, but I am trying to understand it. 

When I start off from a standstill, the RPMs no longer rev high, instead, the transmission engages pretty much right away (i.e. @ low RPMs). The takeoff is smooth and eventually it runs like a champ at speed with clear change in variator as I apply the throttle on straights as well as uphill. This behavior is new and came on this past week. It is not altogether a bad thing btw. I'm just trying to understand what might be going differently on "under the hood". 

N.B. I recently installed both a Gates belt and a DR3 variator with a combination of 10g + 14g (I also installed a 3.5" FrogSkin vent in my CVT case). Initially for the first 50+ miles this combination ran "as expected". Only recently does it exhibit this new behavior.

Thoughts?

Michael

Share this post


Link to post
Share on other sites

Posted

Either the clutch is screwed or a variator weight fell back.

1 person likes this

Share this post


Link to post
Share on other sites

Posted

guess that means I shouldn't ride it until I find out the root cause eh?

Damn fine riding weather these days.

Was hoping the wrenching was behind me for a while...

M

Share this post


Link to post
Share on other sites

Posted

It might be the combination of the two differant weights, read something about this on Adv. Think the guy had a Honda reflex, he ended up going to all the same weight rollers.

1 person likes this

Share this post


Link to post
Share on other sites

Posted (edited)

I  wouldn't think it have anything  to do with the clutch, the clutch is on or off.

Essentially it's Bogging because the CVT is going into top gear from the get go ( there are no gears just a figure of speech)

I would look at the Main Spring, probably  lacking incorrect verbiage but that Main Spring keeps that final ratio low for you to build rpm's and say in the power of the motor getting up to speed. If the Main Spring is Jacked it will allow the final ratio to go up to top gear from the get go..

On the Vari weights, are you using Rollers or Sliders?

If ya have Sliders on or more may have flipped on ya,

Also look for galling on that Pin or Boss or whatever ya want to call it that the Vari slides back and forth from. the Vari has that bushing for that Pin to go thru and evertyt time I service the CVT the Pin is galled and the bushing is nasty so I clean them up with some course scotchbrite and assemble wit a microscopic dot of Synthetic grease, I can feel the difference in how much smoother the Var transitions up and down, and we know the grease or any lube won't last any amount of time and for sure we don't want any lube getting onto or into the Belt

             Good Luck

Edited by pistonguy
1 person likes this

Share this post


Link to post
Share on other sites

Posted (edited)

And to add, that powdered coating coming off along with the roller dust is for sure impending the Rollers from Rolling and now they are Sliding creating the Flat Spots you see.

The Vari just won't work smoothly and or the way its supposed too, again when I clean all this up with round rollers with spiffig the Pin and Bushing the operation of the vary has a noticeable difference of the transition from low to high speed.

 

Even with the 50 miles you have on the new rollers or sliders they may be junk coming apart and all that trash is stuck in the vari..impedeing its proper operation..

 

IMG_1188.jpg

IMG_1184.jpg

Edited by pistonguy
1 person likes this

Share this post


Link to post
Share on other sites

Posted

I just replaced the combination of 10g + 14g sliders with 12g sliders + 12g rollers.

There was some flaking of the teflon to be found amongst the sliders as well as some minor galling of the pin/boss as PistonGuy suggested. At least the ramps are now nice and smooth. I did notice that the part that slides moves up and down smoothly *IF** it is straight. But if tilted at a slight angle, the plastic slides bind to the aluminum posts. I'm wondering if I shouldn't polish the edges to prevent that?

I'll take it out tomorrow morning and report back. 

M

Share this post


Link to post
Share on other sites

Posted

You mixed 12 gram slider with rollers, hmmm I've never heard of that before, most guys say don't mix them, let us know how this works, very interesting , 

Share this post


Link to post
Share on other sites

Posted

Just validated that the problem was in the variator. Not sure if the design/manufacture of the DR3 is the issue or mixing the 10g + 14g was the issue. But for now the 12g mix seems just fine.

Next up I need to install a tachometer so I can establish the ideal weights to use.

M

1 person likes this

Share this post


Link to post
Share on other sites

Posted

So your back on the road, all good.

1 person likes this

Share this post


Link to post
Share on other sites

Posted

Great news

Post some foto's foto 56.

 

Share this post


Link to post
Share on other sites

Posted

did you see any improvement in performance with the DR3 so far? Give us the low down...

1 person likes this

Share this post


Link to post
Share on other sites

Posted

did you see any improvement in performance with the DR3 so far? Give us the low down...

Yes. As mentioned before, I have a long run uphill from a standing stop that I use as a proxy for overall performance. With a set distance the most I could achieve before installing the DR3 was 45mph. With no other changes other than the DR3 I was getting 50mph under the same conditions. So I"m happy enough. Keep in mind I have not "tuned" the variator yet -- I"m using 12g weights with no insight as to what the RPMs are. Next up is to install a tach and then adjust the weights to optimize the behavior.

M

Great news

Post some foto's foto 56.

Sadly I didn't think to photograph the schmuz I found on the variator. So no photos to post. But I will likely be taking it apart again after I install a tach, so perhaps I can redeem myself...

M
 

1 person likes this

Share this post


Link to post
Share on other sites

Posted

Hhahaha yes redemption,  I actually washed my scoot yesterday, looked pretty good, road it up to the golf course today and just beat a thunderstorm home, about 50 mph winds and maybe 1to 2 inches of rain, she was close. When she storms up here it comes quick.

1 person likes this

Share this post


Link to post
Share on other sites

Posted

MJSfoto1956, you make mention of doing a uphill standing start to tune your cvt. I'm still trying to get a handle on these smaller cvt's (I'm pretty well versed on larger snowmobile cvt's. 

Generally "normal" loads would be dealt with by the basic cvt tuning and "abnormal" loads (uphills , unusually hard acceleration , extra weight such as a passenger or cargo) would be dealt with by the Torque Sensing function.

Even though the cvt functions have a combined effect and multi-run comparisons are very important, you may be better off doing your base tuning on flat and level with "normal" throttle.

1 person likes this

Share this post


Link to post
Share on other sites

Posted

 

Even though the cvt functions have a combined effect and multi-run comparisons are very important, you may be better off doing your base tuning on flat and level with "normal" throttle.

I guess it is what it is in my case. I don't have radar. I don't (yet) have a tachometer even. So I chose something that had significance to me: uphills. As long as I can do 50+mph uphill with my scooter I'm a happy camper. Top speed is unimportant to me. Given my requirements, it works. Thanks for the insight though!

M

Share this post


Link to post
Share on other sites

Posted

You know your rpm is safe if your not hitting the Rev limiter, lots of high reving bikes don't even have a tach,s , the new engine control units keep the bikes from over reving.

Share this post


Link to post
Share on other sites

Posted

You know your rpm is safe if your not hitting the Rev limiter, lots of high reving bikes don't even have a tach,s , the new engine control units keep the bikes from over reving.

not sure if these little gy6 cdi's have a useful Rev limiter, anyone knows what the limit might be, the stock one I had got me over 9K when the engine cases came apart and everything went to hell, that was with the 155BBK with a ported stock head and a Nibbi cam.

Share this post


Link to post
Share on other sites

Posted

I've tried to hit my limiter and have never got there, think mine is 9200 or 9400 I just really don't pay much attention to the tach,  my throttle is either on or off hahaha

1 person likes this

Share this post


Link to post
Share on other sites

Posted

This is mine from a couple years ago for that show your top speed thread.

She was spitting oil out the breather at 8,910rpm.

Make sure your up to date and good on the Valve Lash..

 

IMG_1670.jpg

2 people like this

Share this post


Link to post
Share on other sites

Posted

That is good rpm, if I'm not mistaken Piston this is a stock bore, stroke and cam right.

Any update on the variator with the 12g's inside. Did you get to do any CVT tuning, how high is the belt rising in the variator?

Share this post


Link to post
Share on other sites

Posted

That is good rpm, if I'm not mistaken Piston this is a stock bore, stroke and cam right.

Any update on the variator with the 12g's inside. Did you get to do any CVT tuning, how high is the belt rising in the variator?

Ya she is all stock internals, just a high state of maintenance and tune.

I don't have a tune in her now that runs up to over 8,000rpm, sh's tapped out around 7,400 or so and achieving really good belt climb,

Im down around 10 gram rollers, i want to jack with it some more but its like 98 and humid so Im going to be lazy for awhile

 

The belt ant climb a whole lot higher 

IMG_0966.jpg

IMG_1189.jpg

2 people like this

Share this post


Link to post
Share on other sites

Posted

That last 1/8th of an inch might make all the differance hahaha 

Share this post


Link to post
Share on other sites

Posted

Got Damnnn, that is as good as it gets with belt climb. No wonder you were able to pull off those impressive numbers for the top speed thread. Did this require grinding the boss pin for the belt to rise a bit more?

Share this post


Link to post
Share on other sites

Posted

Here are the two together.

Nope not grinding the pin boss but..............Theres Call Outs Comin so Not Tellin...............

 

IMG_1192.jpg

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now