• Yerf Dog Rover 34800 Issues

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 #7886  by wapjr1967
 Sat May 01, 2010 7:46 am
I have a couple of questions.

First... My Rover starts fine idles fine and for the most part runs fine EXCEPT - It does not seem to be able to get up to what I would call top speed. The engine in forward seems to have planty of RPMs but I don't think I am no where near the rated 22 MPH of the CUV. Not that I am in a race to go anywhere. The engine seems to be reving up on RPMs but going maybe 12 MPH. Have changed the Belt , Clutch and Variator(12G rollers) and checked it multiple times to make sure the rollers are properly working and it seems to be ok.

Second -I also recently installed a new tensioner, chain and rollers for the tensioner and I have the chain "fairly snug" but I don't think it is too tight ideas? Could the tensioner SLOW the speed down if it too tight?

Third - Shifting into reverse seems to be fine but shifting into Forward is tough sometimes especially when cold. I know the rpms of the Engine can cause the shifting issues but it still is a little tough to shift into forward even when warm. The idle speed when warm I think is good. Is there a recommended adjustment setting for the shifter cable? How do you adjust it?

Any help is appreciated.
 #7887  by Greyfox
 Sat May 01, 2010 10:41 am
Good morning.
Pghruby will be able to help you out, much better than I.
I just wanted to suggest that you check out the BD Tech Center. There is lots of great information posted. It may help to answer some of your questions.
At the very top of this page is a tab marked "Links". Click on the "Technical Center".
 #7888  by PGH
 Sat May 01, 2010 11:58 am
Top speed: You may have weak ignition, poor fuel delivery or other CVT problems. Start by removing the CVT cover and run the engine on while the vehicle is on stands. You want to look at the belt position in the pulleys and make sure it is traveling properly. Next step is to check your spark - Remove the plug and ground the threads against the engine.You should have a healthy spark otherwise look for loose connections to the coil or CDI. If this is fine, look for a lean or rich condition on the plug. Too lean typically means you have air leak in your intake or clogged fuel filter and too rich is either a clogged air filter or malfunctioning choke.

Reverse: There is fine balance between shifting to reverse and forward. What you described sound like the reverse cable is too tight and does not allow forward to properly engage. Loosen the cable tension half a turn at a time to see if shifting gets better. If your adjust is at the point where the cable is slack or reverse no longer engages, you will need to disassemble your reverse assembly and look for debris or damage.
 #7890  by wapjr1967
 Sat May 01, 2010 9:29 pm
Top speed issue - did find "possible" air leak as the vacuum line for the fuel pump was on but not very tight. also the round "o" ring between the carb elbow and the cylinder head fell right off when i took the elbow off. I also found a crack in the air filter intake elbow so I have repaired that and I am waiting for the sealant to cure before I fire it up again. I did the spark plug test a month ago and it was pretty strong then and I will probably do it again to double check.

What you stated below ( i copied and pasted it ) I only have a forward / reverse shifter on the Yerf Dog rover, It has one Big yellow cable to shift for forward and reverse that runs from the shifter in the front cab area to the transmission in the rear that shifts the transmission f / r. not two separate cables.... other thoughts?

Reverse: There is fine balance between shifting to reverse and forward. What you described sound like the reverse cable is too tight and does not allow forward to properly engage. Loosen the cable tension half a turn at a time to see if shifting gets better. If your adjust is at the point where the cable is slack or reverse no longer engages, you will need to disassemble your reverse assembly and look for debris or damage.


Any thoughts on the chain tensioner that I mentioned in the original post?

btw... thanks for your help!
 #7891  by PGH
 Sat May 01, 2010 9:41 pm
As you stated, there is one cable that shifts the transmission between forward and reverse. If the cable is too tight, it will not go into forward properly. If the cable is too loose, it will not go in reverse.

The chain tensioner would not affect your speed unless it caused the chain to jump.
 #7892  by olderthan
 Sun May 02, 2010 11:17 am
i found that my reverse works better
with my idle around 1000 rpm or
less.i would sometimes hang in reverse
and would have to turn my engine off
to get out of reverse. mine has only
one cable also
 #7893  by wapjr1967
 Sun May 02, 2010 1:17 pm
OK - I have repaired all of the air leaks that i could fine. The spark plug was a little on the "black" side and slightly wet but not too bad. Idles good and pretty solid now even it was not too bad before.

Checked my CVT on Jack stands and it is traveling pretty close to what I would think is normal but I am no expert on exactly how far it should go. Thoughts?

Test drive after it warmed up revealed good engine performance and maybe a slight pickup in top speed but still short of what I would call optimum speed. In other words the engine seems to be getting a lot of rpms but not the speed I would expect from the RPMs.

Does the transmission on these CUVs shift to a higher gear as the speed increases to give more top speed? How does the transmission on these work exactly? That's about the only thing left I have not done anything to.

Again thanks to all for your assistance.
 #7894  by PGH
 Sun May 02, 2010 8:18 pm
Remember that you replaced the stock 14g or 13g rollers with the lighter 12g ones. This will bring up your operating RPM, but brings it closer to your horse power and torque curves. Look in Tech Center section on how CVT's work to see if it makes more sense. If not, we can explain explain it differently so you understand.

http://www.buggydepot.com/buggy-tech-ce ... gines.html
 #7905  by wapjr1967
 Wed May 05, 2010 3:57 pm
seeing that everything seems to be in order as far as the fuel delivery system, it appears that the CVT is my remaining issue with the top speed problem. I will continue to dig into it and let you know what I find. Will the 13g rollers make a difference. They are in good shape and I can put them back in to replace the new 12g rollers. I'll try anything at this point.
Also did you note my earlier question about the transmission. Is the transmission in a CUV multi-stage i.e. does it shift in any manner as speed increases or is it all done with the CVT?

Again Thanks
 #7906  by PGH
 Wed May 05, 2010 4:29 pm
Your CUV uses a Constantly Variable Transmission (CVT). As engine RPM's increase, the weights in the variator push up the ramps to the outside and force the belt higher up the pulley. As the engine slows, the belt will be pulled down into the variator by the torque spring behind the clutch. If you use lighter weights in the variator, it will take greater RPM to "upshift" and result in the engine holding higher revs through its range. The heavier the torque spring, the quicker the CVT will "downshift" when RPM's drop. There is no shifting between set ratios or a set number of gears. The ratios infinitely change from highest ratio to lowest and back without any steps due to belt position on the pulleys.