Problem - FZR250 2KR - Help plz

i have the same prob on my 2kr as well!
i boutght it bak to my mechanic....he had it for 2 days n couldnt get it to stall...
we r both baffled so any help would b great!
cheers...dave

 

mine sometimes does that as well....
even if i have been riding then i stop, when i start it up again after a little while it just stops, so i try to rev the hell out of it and even with full stick it only revs at 2000-3000 for a while then goes back to norm....
only does it even now and then....

 

To flog a dead horse - this behaviour can be attributed to the exup valve not operating optimally, or carbies, or combination thereof. The exup is something that has been discussed in a few other threads, and below are some highlights plus a little of my own.

It is easy check is the exup, and if this can fix the problem then it is great because carbies are not much fun to deal with. I haven't altered my carbies, but a few others on this forum could give advice if you need to (they will probably say go see a mechanic and let them adjust). I have played with the exup a lot (because I originally had the same problem as you), so I can answer that part.

What is the exup? It is a small valve located under the bike (you can see the cover for it when looking under and paste the stand). It causes some backpressure in the exhaust so at lower revs you get a cleaner and more optimal burning of fuel (and subsequently more torque/power) at the lower revs. It should start to open at around 8000 revs, and be fully open at 12 000 revs. The fzr has the optimum power around 12 - 14 000 revs. It is also the main addition to the fzr250 that makes it stand out against its 250 comrades. This valve is on the new r1's, r6's, etc.

What can happen with the exup is that it may not open properly. If it does not open properly it is possible that this backpressure builds up too much and actually doesn't let the right amount of fuel through and subsequently you will stall as soon as you alter the speed / throttle (running rich causes back pressure to build at a faster rate too...). Carbies use the venturi effect to get fuel / air mix through your engine and the venturi effect is very stable when it is constant (i.e. not changing speed), but an increase will cause instability in the venturi effect, and if there is too much back-pressure at this point it could cause too little fuel/air through and subsequently stalling). Decreasing speed won't cause the stalling because since you are reducing the amount of fuel needed the backpressure issue doesn't have any influence (which is why it will happen when you try to accelerate, and not just stopping). I must add a disclaimer that I am not a fluid physicist, and this is my laymans explanation.

The reason why it won't start easily after stalling of this sort? Well the valve is still closed, so the back pressure hasn't been released - very similar in nature to flooding an engine. You can wait a minute or two for it to slowly be released, or you can turn the bike on / off a few times to speed it up. The bike 'calibrates' the exup valve each time the bike is turned on (not started), and this process involves openning and closing the valve so it can help. You will hear a small motor doing this (the servo motor, located under your left leg when sitting on the bike - remove the side fairing to see this). Choke can also help if it has started but not revving correctly yet.

Causes for exup valve not openning properly:
1) the cables attaching to the valve are too loose (which happens with age)
2) the valve may be partially seized, and need a clean.

Checking and fixing the exup Jarmizz style... (thanks for writing this Jarmizz):
*********
Checking the EXUP valve is easy peeze. Take the left hand fairing off just sitting under the sump casings you will see a strange looking thing in the exhaust thats the EXUP valve take that silver cover off ( i think they are 4mm grub screws but cant rememeber to well) and then you will see where the cables meet up with the exup valve. Turn the engine on and get someone to rev the engine and if the cables move the exup valve then its doing its job. You should also when turning the ignition switch to on before you push the start button hear the servo motor do alittle reset sound thats good to hear. If the exup valve dosnt move pull it out of the exup chamber and spray some CRC or WD40 in the moving parts areas they might be alittle sezied from the carbon build up (take off the cables to remove this obviously). Smack it back to getter give her a turn over if it still dosnt move look at the servo motor. Spray alittle WD40/CRC in the cables and if it still dosnt work take it to your local motorbike repairs.
***********
I would also like to suggest a few additions:
- when you take off the cables from the valve turn on/off the bike. The servo motor should move at this point. If not the servo is dead - go to a wreckers and get one is the best option (it could actually also be electrics in this case, so you may want to check there but that is a whole new can of worms so I won't bother discussing here). It is very unlikely that the servo is dead though.
- if you end up taking the exup valve out of the chamber (which can take some effort and perhaps some hammering but it will come out just so you know...) clean it with a wire brush or something else because the carbon may not all come off with crc/wd40. (the valve itself is not fragile, so you don't have to be super gentle with it). Even if it seems to move freely when you play with it by hand it may still be a little tight, so remove it and clean it anyways.
- the exup valve->servo cables should have virtually no slack in them. To tighten you 'loosen' the nuts up towards the servo motor (you will see an adjuster on each cable).
- when adjusting the valve - take an allan key and put it between the 'tooth' on the valve and the hole in the exhaust (you will see what I mean when you look). This is where the exup should be adjusted to according to yamaha specs.

Having said that - I actually have my exup valve adjusted so it is slightly open at rest (the tooth is slightly up from where yamaha states). I have done this because of the problem you have experienced AND I know my engine is running very slightly rich, and this has helped stop my stalling. (I've been busy and not gotten around to adjusting the carbies)

Other things i have found to work/help, if above doesn't solve the problem
1) I have previously unnattached the exup valve (left the cables hanging), and wired the valve so it is open 100% of the time. This stops all stalling, but really degrades bike performance so it is not a recommended solution, but it does work.
2) This is my guideline for city riding that I use (I personally ride the bike in the city between 8000-9500 and follow this guideline)... As you are riding, every once and a while (perhaps every 30 seconds or minute when you are going at a relatively constant speed) - pull the clutch in and rev to about 12-14 000 or so for a second, then let it back down. This will release the back pressure (remember under at 9000 revs the valve is only slightly open, and if your engine is running slightly rich you may not be letting out enough exhaust for how the engine is tuned). This will set you back to normal. Sometimes I will hear a slight dip in the revs, but then they come back to normal - when I hear a dip I often will do this twice in succession and never hear the dip the second time round. Since you are moving the bike actually wants to rev, so it will 'work through' the back pressure issue without stalling. I also rev it the odd time when sitting at lights (this will clear out backpressure again but usually sitting at idle won't be an issue with backpressure. But it can also check to ensure that you won't stall when the light turns green which can be an issue if you have cars ready to move behind you).

The final option, as I said at the beginning, is that you may need to adjust your carbies to run a bit leaner.

FYI: I have found that I can quite accurately simulate this 'phenomenon' if I cruise down a street for about 3-4 minutes when the bike is already warm at a constant 50-60 k/hr in 4th gear (I never have this problem with a cold engine, only warm). I gave it once to a mechanic to have them see if they can stall it and they couldn't, but it is likely because he was accelerating/decelerating/stopping/starting and just generally pushing the bike. I would doubt if he ever cruised a road for 3-4 minutes at a constant at 60 in 4th gear like I sometimes do when city riding. He wanted to find the problem, and to do this usually you make the bike do everything except be constant.

p.s. I have not heard of this problem on a 3ln, only 2kr's. Is this true? If so, then yamaha may have done something to make the 3ln's more tolerant on this issue (perhaps adjusted the carbies differently etc).

 

Could it be the fuel pump. Everytime you switch it to on the fuel pump starts up and sucks fuel from the tank. Maybe your pump is dieing, have you thought about checking the voltage across the pump. Sorry if Boz has suggested this but his post is so long! hahaha

 

ok, im not as much of an expert as some of the other guys here but i have a 3ln and had some similar problems, bike would just die or it would lose power altogether maxing out at 3-4k with throttle all the way back. My fix was relatively simple, fuel line was simply dirty. First time i checked it out, took the tank off, drained the tank, checked all the pipes and cleaned em out. bike started a treat but randomly would lose power while riding. about 3 days later same thing happened, bike lost all power and then would not start at all, not even a push start in 2nd gear. This time i took the tank off, drained the peterol and cleaned the tank out + replaced the fuel filter (its only a couple of bucks so why not?). there were little floaty bits of rust, grit, god knows what else, found a screw, washer and nut in there for good measure. since then, for the past month bike has started first time everytime. Possibly a totally different problem, but may be worth looking into

 

Im having this problem on my 3ln.
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The bike runs fine most of the time, but when im cruising and then come to a stop it tend to play up on me. wont rev up. I can antisipate when its going to happen and if i very slowly open up the throttle it will rev up and then be ok. If I open the throttle quickly it just dies in the arse. Also when starting the bike after its stalled the same symtoms are there, it only starts with full throttle and then wont rev up. I have to start in it and slowly close the thottle and slowlly open it a few times for it to clear. Cranking it for a long time also gets it to start but i still have to open the throttle very slowly the first few times before it comes good. When riding it presents no problem

 

your bike has the exup valve wired open, correct? (I think I read that in an earlier post). If not, try that and see if things get fixed.

A temporary fix to this is that whenever you are just cruising along every once and a while pull the clutch in, rev to 12 000 + for a second or two, and then go back to cruising. You may feel an initial dip in the revs, but after that it will open back up. I always made sure I did this as I was approaching lights that were red and never had a problem.

 

nah, my exup is fine, it was one of the bikes i was looking at brfore i bought mine. I love exup, i wouldnt buy a bike without it.

I was wondering if anybody has, or had their mechanic fix/figure out this problem.

 

im not sure if this is relevant, but does it ever happen when you have a full tank? i mean absolutely full? cos that clicking noise is your feul pump priming and trying to get fuel pressure in the lines... if its clicking for a while, then you dont have enough feul... i had the same problem and i thought i had plenty of feul...

also it couldnt hurt to get your carbies balanced

cheers

simon

 

Try wiring teh valve open for a little bit and see if the problem goes away. If it does then it has something to do wtih carbies running rich.

And following on from Simon's comments - also check the fuel filter as it could be clogged.

 

I had this problem a bit, can be not enough fuel or the carbies. After I had them balanced cleaned and reset the float heights it works allot better. I will have my bike back on the road by the weekend with fresh needles and emulsion tubes so I will see if that has anything to do with it.

 

Found this with a quick search,

http://fzr250.com/viewtopic.php?t=207&highlight=hot+stall

 

mine did that, the shims were stuffed and carboned up, not letting the valves work properly.

 

thanks guys, this has definatley helped heaps, i know know where to go looking first. How do we go about getting that threads good bits in the technical stickies, as it seems to be a common problem