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Discussion Starter · #1 ·
I'm finally getting my 05 660 back together. For the past year Ive been having hell with this thing. I can't get the jetting right or something. After fixing a timing chain issue and having the valves replaced. I still cant get this thing to run with out backfiring at wide open throttle sometimes it even backfires at part throttle. I replaced the fuel filter and fuel lines. Idles fine seems to bog a little when I floor it on take off.

Ive tried the following Main jets Mikuni 155, 160, 170. Im running a 45 pilot jet.

Rhino has larger muffler opening, Uni-filter with no lid, 102 mm piston, mud buster hot cam.

Here is a picture of the spark plug. I'm at wits end here on what to try next.

Thanks
Chris
 

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are u sure u have no header cracks ? i would just spend 160 on a wideband a/f sensor innovate lc-1 on ebay work real good, and will save u a ton of headaches
 

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Have you tried cleaning your carb? It could be that if your passageways are clogged changing the jets won't matter
 

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Backfire on acceleration is lack of fuel and maybe a bad fuel pump, backfire on deceleration is an exhaust leak, Valve sticking open, or Timing! Your plug looks rich on the bottom end, but lean on the top and so I would say Fuel issue! Check the Fuel Pump Pressure!
 

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See my post uner the Engine section called Carb Help. Sound sort of what I was getting when the decomprssion setup wasn't right. Worth a check.
 

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Discussion Starter · #7 ·
This weekend I put my stock CDI Box in while at my lease. Driving around my reverse light was going off and on. When on my Rhino would shut down. So through reading I found some people having the same issue. I think it is the reverse sensor. Riding around it would act up at any speed over 30 mph. The rhino runs strong until this speed then start the backfiring. I'm going to try to ground the sensor as soon as it stop raining. Hope fully this will be my problem. Never notices the reverse light coming on with the procom cdi I have. I also took the wideband out of my race car and it shows it a little lean at idle, rich in the middle and well the wide open just wasn't working.

Ill let everyone know how it turns out.

Thanks for everyones help.

Chris
 

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This weekend I put my stock CDI Box in while at my lease. Driving around my reverse light was going off and on. When on my Rhino would shut down. So through reading I found some people having the same issue. I think it is the reverse sensor. Riding around it would act up at any speed over 30 mph. The rhino runs strong until this speed then start the backfiring. I'm going to try to ground the sensor as soon as it stop raining. Hope fully this will be my problem. Never notices the reverse light coming on with the procom cdi I have. I also took the wideband out of my race car and it shows it a little lean at idle, rich in the middle and well the wide open just wasn't working.

Ill let everyone know how it turns out.

Thanks for everyones help.

Chris
IMO...you should switch from the procomm to the stock CDI with the MSD 4240 we sell for $105 shipped...that will give MUCH improved operation...slightly higher rev limit in forward...much higher rev limit in reverse...and keeps the Stock CDI for all the normal functions like starting and running the dash etc....

You lean low end is due to your 40 pilot jet... you can order a 45 pilot jet from us for $10 shipped...and then you would need a smaller main jet as well...

If you have a selection of main jets to choose from to cover the range between 145 and 155 the pilot jet is all you need...if you need a series of jets you can order individual jets from our website or a mini-jet kit and specify the jets you want...

Very low cost way to get much better results...
 

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Discussion Starter · #11 ·
I already have the main jets and I've installed a 45 pilot. I ordered a Cdi last week.

Thanks
 

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Discussion Starter · #12 ·
Well I grounded out the sensor which made no difference. Did not matter what speed. As soon as I hammer it it goes to ****. Starting lean toward the fuel pump do to all the air bubbles in the lines. Also noticed that the Left port coming out of the pump is not full of fuel and my new fuel filter is not completly full. Looks like it has a lot of air a void in it. What should the fuel pressure be at idle and at wide open throttle? Going to hook a fuel guage up to it.

Thanks for the help.
 

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Discussion Starter · #14 ·
I left the plug on the sensor but I disconnected the wires at the splice and plugged a separate wgrounded wire in to it. I'm going to check the fuel level in the carb bowl tonight. Can someone tell me what size clear line I need to hook to the drain on the carb bowl?

Thanks
 

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I left the plug on the sensor but I disconnected the wires at the splice and plugged a separate wgrounded wire in to it. I'm going to check the fuel level in the carb bowl tonight. Can someone tell me what size clear line I need to hook to the drain on the carb bowl?

Thanks
So which side of the splice did you ground? I hope it was the chassis side!

I would suggest disassembling and soaking the carb to properly clean it. We use purple power. Blowing through passages with air or brake cleaner does nothing and confirms almost nothing. We just had two 660 Rhinos in the shop that had high speed misfires that were both caused by a dirty carb, that couldn't be detected with your eyes or by blowing through them.
I would bet your jets are too big, but I don't think that is the main issue.
 

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Discussion Starter · #16 ·
Can you get the purple power from Autozone or Advance Auto? Also I did the clear hose to check the float level. The gas was below the mating surfaces about a 1/4". I set the float at 13mm like the manual says. Would this be an indication of bad fuel pump or dirty carb? Should I bend the float tab to where the gas is 3/16" or so above the mating surfaces?

Thanks for the help.

Chris
 

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Yes, most auto parts stores carry it.

You could use a small remote reservoir (water bottle, or..) to feed the carb by gravity during a test drive. That will eliminate the fuel pump and confirm or deny it is the issue.
 

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Discussion Starter · #18 ·
Question for everyone. When I had the valves replaced after the timing chain failure. Is it possible or would it make a difference if the machine shop did not out the raptor center intake spring on the right valve? I don't remember if there is a way to verify. Is there a set of springs out there that would work better with my hot cam?

Hopefully I will be able to see if a clean card makes a difference this weekend. Just trying to make sure I have no other issues.

Thanks
Chris
 

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x

dont think you're floating your valves,that wont happen until over 6500 I'd bet, so did the stock cdi make a difference, I had two bad cdi's- finally just threw them in the trash and bought Dynatek cdi's and it fixed the misfire problem I was having, I steer clear of MSD products, they are too finicky in my opinion...if you cleaned the carb with torch tip cleaners and replaced the fuel filter and changed the cdi and changed the fuel pump and set the float level have you checked the return line for the fuel tank? Ive had 3 of my rhinos have a lean problem because the return line was returning toooo much fuel to the tank and starving the fuel bowl. In two instances they started over flowing my mikuni carbs like the float level was too high...another thought, have you lashed the valves and rechecked the lash??..........you might just have an out of adjustment valve??? Never run with an exaust leak too,everything needs to be on the money first.....how dirty is the aircleaner too is an overlooked tuning killer...make sure the pulse line to the pump is tight and has no cracks too...
 

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Discussion Starter · #20 ·
I bought new fuel lines. I've adjusted the float but I haven't put everything back together. The filter is clean. I did try my stock Cdi which made no difference. I have a new dynatec but haven't installed. I just can't figure out why as soon as you go full throttle when driving it goes bad. With it in neutral you can floor it and it's not noticeable. I checked the exhaust by placing a board over the outlet. No exhaust sound change and the rhino stalls out.

Thanks for all the help. Hopefully this long weekend will allow me to figure it out.

Chris
 
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