MV Agusta Forum banner

1 - 20 of 21 Posts

·
Registered
Joined
·
18 Posts
Discussion Starter #1
Could someone please provide some input into my issue I am having , my F4 750 will not rev past 9000RPM , a few weeks back I thought i had solved the issue after cleaning the following :

Air Filter
Changed the fuel filter in the tank
Had the injectors tested and cleaned

Bike is now running on all 4 cylinders but for the life of me will not go over 9000 rpm

This is seriously frustrating ,
 

·
Registered
Joined
·
18 Posts
Discussion Starter #2
just some more information , I also replaced the spark plugs with OEM parts.

Bike was running perfectly fine up until about a month back , so i am certain its not a rev limiter as i have had it over 9000rpm everytime i rode it up until a month back.
 

·
Registered
Joined
·
1,511 Posts
Hi Warre, can you please describe how the bike responds up to 9K, does it slow and struggle up to this point or is it a sudden stop type thing?

One possible cause could be a blocked fuel tank breather, when you replaced the fuel filter did you inspect all of the fuel lines and internal lines in the tank, they can and do deteriorate and may be blocked or restricting flow.

jimboF4
 

·
Registered
Joined
·
18 Posts
Discussion Starter #4
The bike runs smoothly and without any issues up to around 8500 - 9000 rpm , then no matter how wide i open the throttle , she will not pass 9000rpm.
bike idles , revs , and sounds perfect ,
but will not go over 9000rpm,

I did not check the fuel lines , what is the plastic encapsulated filter in the fuel tank ? I replaced the alluminium filter ,
 

·
Registered
Joined
·
1,511 Posts
Hi Warre, the metal canister fuel filter is the replaceable one, it does have direction arrows showing fuel flow, Donsy's free to download manuals show all of this in good detail. The plastic filter is a removable second mesh filter fitted to the bottom of the pump assembly that is a push fit in the base of the fuel base plate. If you pull on the pump assembly the white plastic bit pulls off and you can clean the gauze and refit.

All the the fuel lines inside the tank need replacing every few years, ethanol in fuel can also have a bad affect, check that yours are in good condition and the breather pipe is clear of debris.

jimboF4
 

·
Registered
Joined
·
18 Posts
Discussion Starter #6
Thanks for this information ,
the bike stood for the best part of 10 years , when I bought the bike it had 195km on the clocks , and that was last year June some time , it is now around 3000km ,
I will open the tank this evening again and look at replacing the pipes.
 

·
Cyber SPOTTER
Joined
·
6,101 Posts
How long have you had the bike? Has it ever been past 9k?

It is not a Japan import is it? I understand they have to limit them to 9k for licencing purposes - if so, a second hand ECU (from a non Japan complienced/disignated bike) bolted in will fix all your problems.

Cheers
Rob
 

·
Registered
Joined
·
1,511 Posts
Thanks for this information ,
the bike stood for the best part of 10 years , when I bought the bike it had 195km on the clocks , and that was last year June some time , it is now around 3000km ,
I will open the tank this evening again and look at replacing the pipes.

One thing the early 750 like yours and mine is they do suffer from internal rusting, I have had to strip and clean mine out and line it with a product called "petseal" available on ebay, works well. Good luck with sorting this. By the way the easy way to drain the tank of fuel is to remove the drain plug on the base of the tank.

jimbo
 

·
Registered
Joined
·
18 Posts
Discussion Starter #10
Not a JAP spec model , bike was running well past the 9000rpm mark , until recently.
I am certain it has something to do with the fueling , will look at that this evening.
 

·
Cyber SPOTTER
Joined
·
6,101 Posts
Not a JAP spec model , bike was running well past the 9000rpm mark , until recently.
I am certain it has something to do with the fueling , will look at that this evening.
Ok we can kill that then - does it have any aftermaket fuelling devices like Power commander, dyno jet etc?

I agree with you having ruled out the ECU - one would reasonably expect it to be a fuelling problem.
 

·
Registered
Joined
·
18 Posts
Discussion Starter #12
nope , does not have a power commander , bike is stock standard apart from BMC filter and Blue Flame slip-ons ,
It wont be the pipes either as the bike was running perfectly until recently.

its just so frustrating , and sad to say , , , I found more joy taking my ZX7 out the garage yesterday when i went for a ride.
 

·
Registered
Joined
·
461 Posts
For what it is worth, and I am no expert on F4's, but my 2007 910R would not rev past 9k. When it hit 9k it was like the rev limiter was cutting in early. From what you decribe yours is similar, yes/no?

The issue with mine was the SPU, we swapped it out for one we knew was good, and he presto she rev'd away to her hearts content.

As I say I am no expert on the F4's and I am not even sure they have a similar SPU to the Brutales. However, I would urge you to seek someone local to you (maybe easier said than done, I know) who does not have the same issues as you and try a swap with their SPU.

I hope this may help solve the issue you have, by at least rulling it out, as arguably some of the other suggestions above will be a lot cheaper, although I struggle to see how this would be a fuelling issue if the bike rev's freely earlier in the rev range?

Dave
 

·
Super Moderator
Joined
·
22,070 Posts
as far as I knew , the f4S 750 does not have a SPU " service power unit " ?
Yup, no SPU on there.
This is a shitty one Warren. Tell me, does the bike do it in every gear ?
Does it do it standing still, in neutral ?

As I mentioned before, my bike did this once when I replaced the fuel cap, and it was a blocked breather.
You might have to strip it and go through it all again.

Then we had cases where the 0-rings swelled up and restricted fuel flow, same symptoms.

The last thing could be a bad EPROM or ECU.
I'd look for the fuel issue first, hard to say without seeing what it does first hand.
 

·
Registered
Joined
·
18 Posts
Discussion Starter #18
I seem to think the bike idles perfectly , however my father thinks the bike sounds like it is " hunting " , my father has a SP01 Viper with the same pipes on as mine , however our bikes do sound different , i have always passed this off to the fact that I have a BMC filter and he has a OEM filter.

riding the bike , it pulls " perfectly " up to around 8500rpm then just sits at 9000rpm , almost like it has a rev limiter fitted , however a month back on a sunday ride , i pushed the bike and held it over the 9000rpm mark for long stretches , bike topped out at 278km / h and was running like a dream.

later that day on my way home , running around 200 - 220km /h , as i opened the throttle it kinda just dipped and bike hit a flat spot , was for less than 2 seconds or so and it cleared and pulled normally again

the problem never came back the rest of the day , a week later on my way to a bike rally , was when it just would not run over 9000rpm , it was also running on 3 cylinders ,

I replaced the sparks plugs with OEM parts
I replaced the fuel filter in the tank
I had the injectores tested and cleaned , " injector one was blocked "
I had cleaned the air filter
I cleaned the inside of the fuel tank as there was a lot of sludge on the bottom of teh tank

Bike is now running on all 4 cyliders , but will not run over 9000rpm ,

very very frustrating
 

·
Registered
Joined
·
1,511 Posts
Hi Warren,

Re the sound issue, MV's do idle a nd sound a bit different to other bikes, I don't think that is your issue here, as Donsy and others have said I think this is a fuel / breather issue and I know it's a pain in the ass but you need to pull the tank and inspect fuel tank breather, internal hoses, o rings on the quick connects pulling it all apart and maybe replacing all rubber parts. Good luck and keep us informed.
jimboF4
 

·
Registered
Joined
·
18 Posts
Discussion Starter #20
Hi Jimbo

I am certain its a fueling issue , will be working on bike this evening again ,
my fathers MV Agusta F4 S " SP01 Viper " is 5 engine numbers apart from mine , hence i was making referance to the 2 bikes sounding different as they are basically the same engine + exhaust system , only difference being the air filters
 
1 - 20 of 21 Posts
Top