MV Agusta Forum banner

1 - 20 of 59 Posts

·
Registered
Joined
·
48 Posts
Discussion Starter #1
Don’t mean to take over your thread but found it when I searched as l am having some similar issues. In my case when I turn on the ignition the fuel pump can be heard operating but when I look in the tank a stream of small bubbles can be seen possibly coming from a fuel line until the fuel pump sound stops. Would someone please confirm that this is not normal and if it could be causing the rough running. Am marshalling at Phillip Island WSBK this weekend about 400 k from home. Can anyone offer advice on how bad this may get and possible fixes thanks.


Sent from my iPhone using Tapatalk
 

·
Administrator
Joined
·
19,861 Posts
Don’t mean to take over your thread but found it when I searched as l am having some similar issues. In my case when I turn on the ignition the fuel pump can be heard operating but when I look in the tank a stream of small bubbles can be seen possibly coming from a fuel line until the fuel pump sound stops.
The fuel pump pressurizes the system when the key is turned on, then stops until the ECU receives a signal that the crankshaft is turning and turns it back on. Some bubbles can be normal as there is an open hose for over pressure. #27 in attached diagram.
Now, if you have really old internal fuel hoses they could be deteriorating and leaking, but generally that will lead to no fuel supply to the injectors at all.
Does your engine run?
Capture.JPG
 
  • Like
Reactions: silentservice703

·
Super Moderator
Joined
·
22,357 Posts
You beat me to it, Ed!
 

·
Registered
Joined
·
48 Posts
Discussion Starter #4
Bike starts and idles. But between idle and 3000 rpm it runs rough. Over 3000 it seems to run and accelerate ok. I know the answer is to ride fast but makes it hard around town.


Sent from my iPhone using Tapatalk
 

·
Super Moderator
Joined
·
22,357 Posts
Bike starts and idles. But between idle and 3000 rpm it runs rough. Over 3000 it seems to run and accelerate ok. I know the answer is to ride fast but makes it hard around town.


Sent from my iPhone using Tapatalk

I will assume this bike is new to you. The 1078, and all First Gen MVs for that matter, have a rough low idle and a trough in power and torque below 4000 rpm. This is mainly due to fueling and timing in the ECU that was done for emissions regulations. Most of that can be tuned out by someone who knows their way around the 5SM ECU, or by replacing the ECu with a Microtec ECU.

This has been discussed at length in the forum and a search will reveal the many threads on the subject.

Now, another culprit is low idle speed. Idle speed can only be checked accurately by using the VDST Tool that diagnoses bike issues. The idle speed indicated on your dash is inaccurate for tuning purposes.

You might also benefit from a TPS (Throttle Position Sensor) reset which can only be done via the VDST Tool and software.
 

·
Registered
Joined
·
48 Posts
Discussion Starter #6
Thanks for the replies. Have read a lot of the threads to do with 1st gen ecu and timing. This is a bit worse than power trough below 4K. Bike was running ok until this weekend when it started coughing and spluttering below 3000 rpm. I wouldn’t have thought something would change in the ecu. Might have to look at a tps reset.


Sent from my iPhone using Tapatalk
 

·
Super Moderator
Joined
·
22,357 Posts
Look for vacuum leaks.
 

·
Registered
Joined
·
48 Posts
Discussion Starter #8
Thanks. I’ll try Noel’s thread suggestions re vacuum leaks as soon as I can.


Sent from my iPhone using Tapatalk
 

·
Vendor
Joined
·
5,337 Posts
Bubbles in tank not good,you should only see a swerling action.Time to remove the tank and fuel pump plate,replace internal fuel hoses and filter while you are their.
 

·
Super Moderator
Joined
·
22,357 Posts
Done
 

·
Registered
Joined
·
48 Posts
Discussion Starter #12
Finished marshalling at Phillip Island WSBK unfortunately including helping pick up Randy Krummenacher's crashed MV. Went via the Alpine highway on the way home. Unfortunately it poured rain on the way down from Mt Hotham with fog reducing visibility to about 5m. Rough running at low rpm didn't improve although it wasn't as bad when the bike was cold. I'm now trying to remove the airbox on the 312R to check for vacuum leaks. However I cannot remove the left hand air box retaining screw. It is partly undone but now the rubber well nut just seems to spin with the Allen screw. I have tried wrapping wire around the screw head and pulling whilst unscrewing to attempt to apply pressure to the well nut to hold it in place without success. Last time l had the airbox off the well nut was loose so I attempted to glue it in place. Obviously failed. Unable to find related threads. Not sure what to do now. Any suggestions?
 

·
Super Moderator
Joined
·
22,357 Posts
You could get a sharp narrow pick and slide it into the rubber part of the well nut. Sometimes those nuts will corrode just a touch and bind them to the bolt.
 

·
Super Moderator
Joined
·
22,357 Posts
Just to be sure, you are having difficulty with part number 21, not part number 11, right?

476290
 

·
Registered
Joined
·
48 Posts
Discussion Starter #16
Yes it’s part number 21. I have already replaced part 11 with rivnuts as suggested on the forum


Sent from my iPhone using Tapatalk
 
  • Like
Reactions: silentservice703

·
Registered
Joined
·
48 Posts
Discussion Starter #17 (Edited)
Cannot get a small flat bladed screw driver in to hold the wellnut. Was able to get a narrow dental pick into the wellnut but couldn't hold it. The nut seems to be stuck on the Allen bolt and is spinning inside the rubber part. Unless something else comes up am at the point of trying to cut the head off the bolt off with a Dremel cutter and trying to push the rest back through the frame. Just concerned this approach may make things even more difficult if further problems are encountered.
 

·
Registered
Joined
·
14,510 Posts
2 Methods;
1. Use a real penetrant on it .....best tested, 50/50 mix of automatic transmission fluid and acetone, from the guys on the North Sea oil platforms
2. Hold the head of the bolt with ViseGrips, use a 5mm drill bit (or a #9 in the US)
And drill the head off
If you drill it, push the remaining piece in with a Phillips screwdriver and slip a thin
piece of metal behind the frame tab to protect it
 

·
Administrator
Joined
·
19,861 Posts
Like Noel said, drill the head off. Those well nuts are a special hexagonal outer shape. MV has them in stock and they aren't that expensive.
I replaced mine because the outer surface had mushroomed over time making getting the air box back on difficult.
 

·
Registered
Joined
·
48 Posts
Discussion Starter #20
Unable to free nut from bolt so reverted to a combination of drilling, dremel cutting & gentle persuasion with a punch to finally remove the air box. Frame may need a bit of a touch up.
 
1 - 20 of 59 Posts
Top