02 Honda Foreman Rubicon 500 engine or tranny issues

[TheRetiredMilitaryGuy]

Hey y’all, I need some help badly. I have a 02 Honda foreman rubicon 500, it sat for a year (ran out of time) just did a full top end plus piston and rings on it. Got it running but it will not drive forward at all and will only do 2 mph in reverse. The engine or transmission makes a very loud whining when I hit throttle both ways. 
I need some help I’m very unfamiliar with the hondamatic. 
 

Any ideas or options?

[spock58]

I also own a first gen Rubicon that had a similar issue. After dealing with any diagnostic/fault codes (gauge will flash) the unfortunate outcome was a failed hondamatic with mine. Honda does not sell parts to fix them, it's only sold as a complete assembly. The oil pump was usually responsible for the transmission going bad so this part needs to be updated as well. It is a big job to complete and the parts will be very expensive if you go with new. That's what I did since the quad was in great shape otherwise.

[Gwbarm]

I would change the fluid, sounds like something is stuck, if it was shifting good before you parked it, sitting should not have caused this problem.

[Mech]

I tend to agree with Gw that if it was going it should come right. I  think the first thing I'd do is leave it running till it got completely warmed up, trying the gears every few minutes. Things like this happen to things that have sat for a long time, and sometimes they come right once the engine has fully warmed up and had whatever limited operation is possible.

Other than that, did you do this work in place or with the engine out ?

I presume that the gear position indicator on the dash is working correctly ?

And when you give it throttle, the engine does rev as it should it ? The engine performance seems to be right, it revs quickly in neutral and idles well ?

When you rev it does forwards seem to have any drive at all ? Does it try to load the engine or creep forwards ? When it's in reverse, despite it's limited speed, does it seem to have some power to it ? Will it reverse up a slope say ?

Have you checked the oil pressure ? The transmission needs good oil pressure. Changing the oil and filter might be a good idea.

If you can take a video of the noise from close to the source it might help..

Edited July 7, 2024 by Mech

[spock58]

It's also possible that the chain that drives the oil pump has stretched enough that it fell off the sprocket. This would cause a failure to drive as well. The chain is found behind the front crankcase cover near the centrifugal clutch.

[Mech]

A couple more questions..

How long was the engine disassembled for ? It hasn't sat opened up for a year has it ?

And did you run it after the year sitting and before the engine work, and was the trans working then ?

[Gwbarm]

Chain is a good possibility, the next thing i was going to suggest is the pump pressure and stuck bearing.

[Mech]

Hopefully poster #1 checked oil was getting to the cam after the overhaul. Most manuals say to loosen a bolt somewhere and bleed and check the oil supply to the top end after work like that.

It has to have some oil pressure to make it go in reverse. I'm pretty sure if the chain had come off nothing would work.

If the oil pressure to the trans was low though it might give very reduced drive which may only have enough power to drive in reverse which in most things is a very low ratio. That's why I asked if it would drive up a slope in reverse, and whether there is any signs of drive at all in forwards.

 

[Gwbarm]

Good point!

[Mech]

It goes centrifugal clutch - variable ration Hondamatic - forwards/reverse box.

It would seem that either the centrifugal is slipping or the Hondamatic is seriously down on power. I'd be pretty sure that the only going in reverse is a red herring. Reverse is probably a lower ratio and so manages to move the bike.. 

The noise..  That's a mystery, and I also suspect, not really the cause of the lack of drive.

So.. Is the engine down on power, or is it the clutch/Hondamatic.

All my questions are always for a reason.. I consider all the possible causes, eliminate what possibilities I can, try to devise a test that will differentiate between the other possibilities, then try to devise a test that will always consistently reproduce the problem, and that will hopefully be the only thing or combination of things that cause it..  Then I know how to reliably test I've fixed it after the repair.  That works every time in real life and when I do it.. haha.

[TheRetiredMilitaryGuy]

On 7/7/2024 at 3:30 PM, Mech said:

I tend to agree with Gw that if it was going it should come right. I  think the first thing I'd do is leave it running till it got completely warmed up, trying the gears every few minutes. Things like this happen to things that have sat for a long time, and sometimes they come right once the engine has fully warmed up and had whatever limited operation is possible.

Other than that, did you do this work in place or with the engine out ?

I presume that the gear position indicator on the dash is working correctly ?

And when you give it throttle, the engine does rev as it should it ? The engine performance seems to be right, it revs quickly in neutral and idles well ?

When you rev it does forwards seem to have any drive at all ? Does it try to load the engine or creep forwards ? When it's in reverse, despite it's limited speed, does it seem to have some power to it ? Will it reverse up a slope say ?

Have you checked the oil pressure ? The transmission needs good oil pressure. Changing the oil and filter might be a good idea.

If you can take a video of the noise from close to the source it might help..

 

Edited July 9, 2024 by TheRetiredMilitaryGuy

[TheRetiredMilitaryGuy]

I did do the work in place on flat ground. 
Yes the gear indicator is working lighting up neutral. 

The engine revs just fine in neutral. When in gear it seems like the engine has little load put on it  

When in high and low gear it acts like it wants to drive, but after 1/8 throttle it begins to whine.  It'll try to move, with a small push it will barely move on its own.  But then stops. 

When in reverse it was only on flat ground.  But once it gets to 2 or 3 mph the whine is loud, I stop when it got loud  

Not gonna lie not sure how to check the oil pressure.  But I did check the oil level and it may be a little over full. 

How would I check and make sure the oil pump chain is good. 

Here soon when I get back to it I'll take a video of what it's doing.  Just gotta work around the farm projects.

[Gwbarm]

Do you have any error codes showing up, i was thinking maybe bad connection aat the angle sensor, but that should show a code.

[Mech]

If the neutral light is behaving normally it shouldn't have any codes.

Ok TRM.. First thing you should do is check the oil pump is working. The easy way to do that, and what they recommend after working on the top end, is undo a nut or bolt somewhere on the head to make sure oil is pumping out. The service manual will say which bolt, or if you know which head stud or gallery the oil gets up going to the head you can generally make an educated guess. The oil check bolt nearly always has a copper washer which is a give away. If you can't find the bolt, pull a valve cover off and make sure there's plenty of oil in there.

The second thing you need to do is what they call "initiate" the ecu. After the carb has been disturbed, or the ecu changed or a few other things being done, you need to go through a procedure to allow the ecu to check and adjust it's running parameters.

It's also possible, (you didn't say whether it sat opened up for a year) that the gear ratio changing mechanism is stuck. It's operated by al electrical motor and when you turn the key it should be able to be heard moving as it sets the ratio at start-up. The initiation process says to listen for the electric motor operation is step 7 also. Check that because if it was in a ridiculously high ratio it might give some of your symptoms..

At this stage, according to your descriptions, I'm suspecting the centrifugal clutch..  I'll have to have a read up about how that model applies engine braking, but hopefully it will be possible to test the centrifugal clutch without taking it to pieces.

[Gwbarm]

The whine does sound like oil pump, but there is a bearing in there that has a plastic ball separator, hope the bearing did not get stuck from sitting and break that plastic piece that hold the balls in place. That is a non replaceabe part.

[Mech]

oops. Forgot to attach  this..

Rubicon initiat.pdf

Yeah if it sat open for a year it could have rust on things..

[Gwbarm]

Thanks for posting the PDF i had forgotten the exact sequence you push the buttons to reset everything.

[Mech]

I hope that's the right way.. In here before, someone was trying to do the initiate and it wasn't working, then we found a different method in another manual and it did work..

If that method doesn't work TRM let us know and I'll hunt out the other manual.

[spock58]

On one of these Hondamatics I worked on, it sure acted like the centrifugal clutch was at fault. When the engine was cold, it worked normally but once warmed up it acted like clutch slipping. It wouldn't go very fast and uphills were not happening. Removed the clutch and it looked fairly burnt but not really worn out. Installed a new one and there was no difference, still slipped when hot. Ended up replacing the Hondamatic to get it working right. These transmissions are pretty reliable and have been in use for years but they can fail, especially the ones in the first couple of years before Honda updated the oil pumps. Unfortunately, there are many sensors & motors & electronics involved that lead to difficulty with troubleshooting.

[Gwbarm]

it ashamed there are no replaceable parts in the hondamatic, it probably is the pump. Hopefully something is just stuck and  it will come around.

[Mech]

The pumps are like diesel injector pumps, or even more like the variable displacement hydraulic pumps in excavators. They have very precise plungers in very precise bores and no seals of any sort. They should last for a long time though. The pump, and it's attached hydraulic motor(which is much like the hydraulic motors in excavators), is a very simple piece machinery that doesn't really have much to go wrong with it.

The previous poster that was having trouble with his Hondamatic also had a squealing noise. That one came right eventually without replacing the trans unit.

I'd highly recommend diagnosing what the problem is before committing to a new trans on a hunch !

 

[Gwbarm]

I completely agree, very curious to know what the problem is.