johnson-question about alarm that lowers rpm

[cookiesareyummy]

Please check post 8 for a better description

J90PXSRS. I have to get the year but will update that later, and this is a bombardier.

I could run this engine at full speed for about 5 minutes (it runs great) but suddenly it starts to sound and feel like a few cylinders are being cut out. I shut it down and sit for about half a minute, start it back up and bring it to full throttle and it runs great again for a few minutes then does the same thing. I know there are some alarms that will drop the rpm so you don't hurt the engine but am wondering if this could be narrowed down or not by the description.

 

[cookiesareyummy]

Re: johnson-question about alarm that lowers rpm

I forgot to mention that the VRO system was removed and has been working fine without it for a long time now. I'm assuming the safety feature for that won't be kicking in. The only other thing I can think it might be is an overheat thing killing the rpms even though the engine is not overheating.
Those are the only two things I can think of that would keep the engine from going above a certain rpm.

 

[wilde1j]

Re: johnson-question about alarm that lowers rpm

How do you know it's not overheating? Is the horn sound constant?

 

[cookiesareyummy]

Re: johnson-question about alarm that lowers rpm

No alarm actually comes on. I'm sorry I posted that in my title I just didn't know what else to call it. But no alarm actually comes on it just gives the symptoms of a cut in rpms like you would have when the engine tries to keep the operator from going to fast when there is something wrong. As far as it not overheating, the temp gauge is working fine, plus I did pull the cover and feel the engine which felt fine.

 

[ezeke]

Re: johnson-question about alarm that lowers rpm

You don't have S.L.O.W. on that engine.

Several ignition components can break down once they heat up, and the engine could bind if it is overheating. Either could cause your symptoms.

You may also be running your float bowls dry, which I would check first. Start at the fuel tank and work your way out. Eliminate redundant fuel filters, angles in the lines, dirty filters and pickup screens, old anti-siphon valves, blocked tank vents.

 

[Dhadley]

Re: johnson-question about alarm that lowers rpm

Does the alarm go into self test mode when the key is turned on? (brief beep)

 

[cookiesareyummy]

Re: johnson-question about alarm that lowers rpm

S.L.O.W. is the word I was looking for, thanks. I will double check on the beeping when I turn the key on. I'll see what I can find with the fuel lines and I'll run it with spark checkers to see if it is actually loosing spark, problem is I have to do it at full throttle so won't be able to update till I am able to do that with someone.

 

[cookiesareyummy]

Re: johnson-question about alarm that lowers rpm

Ok here is an update with more accurate symptoms. I ride around out there doing full throttle with the engine running beautifully for a few minutes then it starts to break down (sounding like an ignition miss). I can lower the rpms and it will smooth out nicely, I don't have to lower the rpms all the way for this just a bit. But if I bring the rpms back up it will start to break up right away. I shut the engine down start it up within a second and I can go right back to running full throttle for a while till it decides to break down again.

I checked spark at all cylinders while problem was happening. It was hard to see the spark so instead I pulled each plug one at a time and each time the engine reacted by smoothing out a little bit when the plug was pulled and went back to sounding the same when the plug was put back on.

As far as checking to see if the float bowls were getting empty I was only able to see that after shutting the engine down and loosening each float bowl screw and plenty of fuel came out of all of the carbs. I also tried to pump the primer ball while the symptoms were going on but had no change.

When I turn on the key the engine does beep but there is no beeping going on with the symptom. I also double checked the temp with a temp gun which was fine and changed both the remote filter and engine filter.