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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.
 
#146 ·
If valves are going to stick open it will happen after the engine hasn't been cranked in a while, not straight after its been just running. Also if someone has fucked up the timing and torqued the cam caps down and pushed a valve on lobe into the piston it shouldn't run properly from startup. Plus only 1 cyl would have bent intake valves. Which 3 valves on which cylinders were the bent ones?
If it was caused by heat from valve adjustment you should see evidence on the seats, heat from detonation should kill exhaust valves first.
How badly were they sealing? No comp at all or was there a little bit in the affected cyls? I would have thought that valves only slightly warped like that wouldn't cause the engine to not start.
When u checked for fuel was the injector spray strong? Reason I ask is that if ur fuel feed line comes off intank ur injectors will still squirt fuel out from gravity acting on the higher tank. Not enough to start the bike though.
I really can't see how 3 intake valves would warp so badly as to cause no start from just moving the bike.
Maybe they have been like that for a while and arnt the cause of the non start issue?
 
#147 ·
G,day Carl.

Put this problem to bed once and for all.

Get as set of " V " blocks and lay your valves in them and check the stems and valve faces for concentricity using a dial indicator.

then check the stems for size and then with a bore gauge check the guides. This is the only way , without sending your head into the shop , to have any certainty everything is o.k.

I would not put new or refurbished valves back into a non checked valve guide.

As a rule , if you use refurbished valves or use replacement valves they will need to be machined/reseated into the exisitng seats.

Just for the worth of mentioning it and not knowing other peoples degree of mechanical knowledge , if new guides are fitted the process of recutting/replacing the valve seat in the head must then be carried out.

each time the guide is fitted it will have a slightly different centre point compared to the previous guide.
If you were to drop a valve back in to this new guide the chances of it sealing up 100% is almost non existent.

Did I read somewhere in this thread this bike had recently come off the Dyno. If your valve springs are a little weak or the engine over revved then it may have got valve bounce. At 14,000 + rpm a little tap from the pistons on the valve face will be more than enough to bend the stem.

Last note , I think the evo2 and later , along with the SPR use a thinner valve stem . the idea behind this was to make the valve gear lighter giving better performance BUT there is a trade of...strength of the stems.

Good luck with your next stage.
 
#149 · (Edited)
Yes I know this is an older thread but as I am a new MV owner I have been reading through many posts and learning about MV's and specifically the SPR. I have read through this entire post and may be able to shed some light on the failure.

The valve failure you have experienced is known as "tuliping". It is more common than you think. I have seen it quite often in boats (I was a boat mechanic in a previous life). It results from the valve overheating and the hammering by the spring causes the valve head to deform and warp. When really bad it does look like a tulip. It occurs on intake valves too as they are often not of the same material as exhaust valves and will fail at a much lower temperature. Thin, lightweight valves are more prone to this.

As I mentioned the cause is that the valve got too hot. In boats this is generally caused by a lack of cooling water but running lean is a common cause as well as detonation from low octane fuel. Over-reving or sustained high rpm when running hot is a sure killer. Once it gets even a slight bit warped the valve is no longer in full contact with the valve seat and therefore is not cooled by the head and things go rapidly downhill from there.

My guess is that your valves failed from a lean condition or perhaps detonation. Since I cannot examine the parts closely I cannot tell if there are the signs of detonation or not. A small vacuum leak on one (or in this case two) cylinders is a common cause as is a partially clogged injector.

I hope this helps someone.
 
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