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non start issue. Win a free MV Corse carbon fiber key guard

13K views 148 replies 32 participants last post by  Cybeeria 
#1 ·
If you correctly diagnose the problem, I'll send you a genuine MV Corse carbon fiber key guard for an F4.
Bike was running fine after the chip replacement. It started this morning as I was loading it onto the truck and died. Never started after that. It turns over, it won't catch.

There is spark.

There is fuel.

The ECU is fine, I tested it on another bike.

The TPS was cracked, from my leaning the bike against the door jamb, probably, but I fixed it. I even replaced it with another one and still no joy.

Ask as many questions as you like. This issue has me stumped.
 
#75 ·
The problem appears to be solved and the only two things I did that can account for it are cleaning a little carbon off the valves hoping they would seat and changing the spark plugs.

I have to go back through the thread, but I don't think anyone suggested carbon on the valves so the key guard goes to the first one who suggested spark plugs.
 
#78 ·
I was thinking it was tire pressure......did I win?
 
#84 ·
carbon on the valves could be a problem, but I'm willing to bet it was the plugs being questionable and wet making it not start. You have to have a pretty killer ignition system to spark an engine with wet plugs especially if they aren't fresh. I'm glad you got it running
 
#87 ·
Carl,
Visit your friendly Yamaha dealer and get some Ring Free....follow the instructions for a shock treatment. It will clean up your valves and combustion chambers.
Mercury Marine also has a product called (I think) Instant Tune-Up. It's an aerosol that you spray into the intakes on a fast idle. The engine will stall out and then you let the engine sit for 15 minutes. When you start it back up it will fog the neighborhood for mosquitoes but there will be no deposits left in the combustion chambers. This stuff really works!!
Only problem is you will have to replace the spark plugs to restart the engine.
And both products will require changing the oil afterwards.

I've used both with good results. The Mercury stuff is the most aggressive and fastest method.
 
#89 · (Edited)
Dyno flogging went like crap. The bike is way down on horsepower and sounds like it is back to running on three cylinders. there is no fuel off idle. It is off the chart lean. Once you get on it, the fueling is actually pretty good and it is probably running on all 4 since the hp is around 108. Down about 15hp from the other SPR.

Compression after our little run was still all over the place. It went up 20 psi in cylinder 1, down 20psi in cylinder 2, up 5 psi in cylinder 3, and up 30psi in cylinder 4. So, all the cylinders had more compression across the board, but number 2 instead of number 4 is way down.

Lets go back to guessing what the problem could be. Sorry, no more free keyguards, but I probably could find something else.
 
#92 ·
Its either rings or valves, can't be anything else. If the mileage isn't high then the probability is that it has to be leaking valves. The reason they are leaking I don't know possibly burnt seats. (possibly caused by tight cam/valve clearances)

Check your valve clearances Carl it may be indicative of the possible cause.

Whats the mileage on the clock?

:popcorn:​
 
#94 ·
i'd go in order from cheapest to most expensive fixes. Since this seems like the compression is funny, i'm with Ade on it having to be valves or rings. Try using the stuff that Ed mentioned first before tearing into it. Worst case I know someone willing to take on the project
 
#96 ·
OK.....look guys, he has to fix the compression first. Period. Engine won't run for crap with a mechanical problem.

Carl, buy a leak down tester....or you can use mine when you get here in a few weeks. That will tell you where the compression loss is coming from.

You may have injectors partially blocked by dead gas residue. There is a service in Wilmington NC that will test, clean and graph the flow rate for $20 each plus shipping there (they pay the shipping back).....but that doesn't fix the low compression.

The Mercury Marine product I was referring to is called Power Tune. That would be my first line for the compression question....if it is still low and all over the place then the leak down test will point you in the direction you need to go when you take the top end apart.
 
#97 ·
I know where it's leaking from. It's leaking past the valves. With the throttle body off, I can place the palm of my hand over the opening and feel the air. Not just a little air, a lot. If I bear down with all my weight, I can get the air to force it's way up the valve stem and out the top of the head. I know the valves aren't sealing well, but I don't know why.

I find the Power Tune and buy it asap. I shall report back with results.

Yes, I will be there in a few weeks. I have changed my signature to reflect the transition.
 
#99 ·
My money's on clapped out valve seats and worn guides. Methinks you need a complete valve job. Mic the stems and guides to check for clearance problems. Worst case new valves and guides if the guides are replaceable. Have to redo the seats and valves at the very least. Got stem seals on the guides?

No need IMO for a leakdown. Pretty obvious what's going on.

Build a boat. Alot less grief. Hah!
 
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