Problem: Engine cutting off

[Balkan boy]

Bike:
2013. 400RR. 140h. 4400km. Regularly maintained. (almost entirely stock)

Symptom:
I push the start button and the engine starts. I touch the throttle and the engine cuts off. I start it again and it runs OK. This doesn't happen every time. Sometimes it happens when the bike is stone-cold, but more often when it's warm/hot.
Sometimes I start it, rev it a bit, but when I put it in first gear it cuts off. Sometimes I can hear the engine started kind of weak, and then it happens. Most times there is no indication. It also happens the most when I get stuck in a difficult stop-and-go section. Engine never cuts off when riding, and the bike is powerful and good overall.

This issue started about 20h ago. At first it was a nuisance, but now it's happening more often. Now it will happen a few times in a row, while in the beginning it would occur once, and then the engine would run OK.
I thought it were the valves, so I adjusted that (one intake was tight), but it did not affect the cutting off issue.
Now I'm suspecting it could be a dirty carburetor. My fuel consumption has also been high for a while.

I would appreciate any suggestions or tips.

Cheers.

[twowheels]

Might be electrical ... an intermittent kill switch short perhaps.

[ricoyam]

I would have checked the carb before thinking you had a mechanical engine problem. High fuel consumption should tip you to a fuel system issue too. Clean the fuel tank and petccock too.
The FCR is a great carb but can be very trying when things go amiss. Check the vacuum break plate and replace the o-ring. The plate wears over time and the o-ring will swell becoming difficult to impossible to get it back in place.
I like to recommend a Flex Jet too while you have the carb off and apart. They make tuning so much easier.
Make sure the enrichener is shutting fully too.

While you have the tank off check electrical connections. Also check that all the grounds are paint free, clean and tight.

[Balkan boy]

Thanks for your opinions.

It doesn't feel electrical. I've checked the kill switch and all the connectors behind the headlight, and everything is clean and dry.

I've recently put the stock tank instead of the IMS tank, so I think it and the petcock should be pretty clean.

[ricoyam]

So did you get the carb off yet?

[Balkan boy]

So did you get the carb off yet?

Not yet.
That carb is a bit over my head, so I'm going to take it to a mechanic.

I'll do another test to try to diagnose it more closely.

[Balkan boy]

Small update.

I got an idea that the engine may be cutting off because of spent gearbox and clutch oil.
I've checked the log, and this issue coincided with putting Motorex TopSpeed 10W40 oil in the gearbox.

I've drained it, and it was the consistency of mud or spoiled milk. Gray in color and not looking like oil.
Previous oil change was Motul 300V witch came out almost like new after 50h.
I was kind of glad, thinking that this may solve the cutting off, but as they say, correlation does not imply causation.



I put in Motul Transoil Expert 10W40 and went for a small test, but the cutting off is still present like before.
I'm going to test it one more time before giving up on the idea.
I'm not convinced it's the carburetors fault.


Cheers.

[dirtbird]

Did you check coolant level/condition?
Also check water pump impeller and bushing.
Not the answer to your problem though.....

[ricoyam]

Could be a head gasket or cracked head. Coolant is getting into the oil. The milky looking oil is emulsified water.

If the carb is too much for you this is going to be worse. Take it to your dealer.
It wouldn't be a bad idea to take this opportunity to learn about working on your bike.

[Balkan boy]

That would be scary proposition.
I check the coolant from time to time, and radiator is always filled to the tap. It's that expensive Motul stuff, and about a year old now. Bike runs pretty cool. I can crawl along in first gear for a long time before the fan comes on.
How much coolant would it take to cloudy up the oil?
Bike was upside-down recently after a gentle tip over.