I have a rubi that has made a grinding noise while going downhill or just coasting along at speeds under 8 mph. It has done this since I bought it in '03. If you gas it the noise stops. It had 100 miles on it when I bought it used and has less than 2000 now.

It only does this after its warmed up.

A couple of years ago I tried to find something on this, and everone said it was the hondamatic. I balked at replacing it then because I found many posts where people had this replaced and it did not solve the problem. It still runs great and shifts up and down fine in d1, d2, and esp. So I never messed with it, figured if it died I would mess with it then.

I did check the sprag on the clutch some time ago and it functioned fine.

Lately I have heard that is a well known problem on the early rubi's with some type of valve near the oil pump that was faulty when manufactured.

Does anyone have any info on this, can this valve be replaced, or is it a part of the oil pump, and if you had this problem did this solve it?

 

mine does it when it rolls with the engine off, and a bit when in low range with ultra heavy loads pushing it downhill

 

Are you sure it's a grinding noise? Reason I ask is that my 07 Rubicon, bought used in mint condition with only 49 miles on it, makes a noise when started that is more of a "whirring" sound, no doubt due to all the internals in the transmission spinning around.

 

I've never noticed if it does it with the engine off, can't actually say that I have been in a situation with the engine off to notice.

Yes, its a grinding or ratchit type noise and its gotten louder over the last couple of years.

I started to think it was normal for the model until I rode a friends and his doesn't do it. Again, it doesn't start doing it for a while, usually after its been running for an hour or so.

 

My guess would be the sprag clutch isn't holding under load, though it may feel fine when you check it by hand.

I think I'd also check the driveshafts and other stuff, including shift linkage.

I also remember a post a while back about an updated ECM for the Rubicon to correct some sort of software glitch with the transmission.

 

I finally met a Honda Service Tech who knew exactly what I was talking about yesterday.

He said that after warm up the oil will lose some viscosity, and on this ATV the oil pump doesn't provide enough pressure when idleing. This was a well known problem on the Rubicons.

The problem with this is the engine case has to be cracked to replace the oil pump, and if your going to replace it the Hondamatic may as well come out at the same time because there is no way to tell if it has any damage.

The parts and labor for this usually exceeds the value of the ATV.

His suggestion was to idle it up when I hear the noise to pick up the oil pressure and drive it till it dies, then scrap it.

I'm curious as to whether or not running a little heavier weight oil would help.

Has anyone tried this, what weight oil did you use, and did it help?

Also, This ATV still looks as good as new, we have a full shop where we rebuild our farm equipment all the time. I would have no problem with spending the $1400 or so on parts and doing it myself. Has anyone done this job, could this job be done by the home mechanic? If you have tackled this I would like to know how it turned out, and what kind of advice you have.

 

The hydrostat unit I think has to be replaced as a unit.

Taking the machine apart for those repairs wouldn't be that big of a deal if you have rebuilt engines or motorcycles before.

A factory service manual would be a good investment.

My friend runs 10W40 in his with no problems. Being a dry sump, to get an accurate oil level you have to let the machine idle for about 5 minutes and then let it sit for a minute or two.

Let us know how it turns out.

 

Update: After reading my Clymer manual I noticed that you can run different weight oils based on temperature, everything from 5W in extreme cold climates to 20W-50 in extremely hot climates. 10W-40 being the norm.

I figure if its an oil pressure problem on this atv when it gets warmed up, why not try a little thicker oil.

So I changed the oil and filter replacing it with 15W-40.

That was 2 weeks ago. The temp here has been upper 60's to mid 70. I have run the Rubi pretty hard several times for up to 2 hours at a time, and every day for a least an hour.

So far the grinding noise is GONE.

I'm inclined to believe that the problem is the oil pump on these early ones was not up to par. Now I'll have to figure out if I run it as is until it goes out completely, it could last a couple more years, or change out the oil pump.

 

Same noise in my 2001 Foreman Rubicon since I got it 4 years ago. Scared me at first, now I am used to it. Will change out the oil and see if that changes anything.

Noticed JeffTD posting here and on another topic that is also causing me grief. Since we both run Cummins diesels thought I might ask another question.

Fuel drains out bottom of ATV carb when first turn the gas on, either reserve or regular gas setting. Seems to stop after ride a while, but scary starting off with puddle of gas under the bike.

Took the bike to local ATV repair shop and they cleaned carb.
Seemed OK for a while.

Started again so took it to Honda dealer and they claim they rebuilt the carb, but as soon as got it back it started right back. When I complained they said only option was to replace the carb with a new one.

Any advice? Thanks for these forums, glad to know I am not only one with these problems.

 

On the Rubi - my advice would be to drive it into the ground - but to change the oils on schedule without fail. Always idle the Rubis before starting off, and don't give full throttle till oil warms up.

On the carb - the shop probably didn't rebuild it , just cleaned it. To be sure you would be best cleaning out the tank, and then to use a funnel with a filter in it when filling. Last month we had 8 customers inwho had all filled at the same gas station with contaminated fuel, showing same symptoms as yours.