VFR after market can

[killa]

As you know I got the VFR I wanted.
I was out on it yesterday having a blast round Cheltenham, I was doodling along with a shitty Golf GTI right up my ass (I appear to be getting a lot of grief on the VFR from twats) so I thought I’d get some ground between us. Took the thing to 13 grand on the rev-o-meter and slowed down. The bike stared to sound like a bulldog being drowned rather like a Ducatti, I was loosing power so I pulled over.
The bike was ticking over fine, first thought was one of the plugs is missing, switched it off, started her again went first time. The bike seemed fine, got my mechanic round any way and he rev the tits off it stood still, as I did before and the same thing happened, same rumbling noise.
He says it is the end can I have on there, kind of messes up the set up as it hasn’t been jetted etc.
This sound right to you?
I am really paranoid at the moment so I thought I’d get some opinions.
____________________
Cleverly disguised as a responsible adult.
Bike:- Yamaha TRX850 | Killas Biking History | Killas Gaming History | Killas autmotive history

[Robby]

So you give it some stick and it starts firing on two?

Several possible causes, most likely electrical though, particularly on a VFR400.

First thing to eliminate is the can making a problem. Seeing as pretty much every NC30 on this forum has an aftermarket can, and to my knowledge most or all of them are on standard jetting, I'd rule that out. Maybe if its a very free flowing full system and you have a K&N or similar air filter its leaning out too much, but I find it unlikely.

What speed was this happening at? At 112 mph (180kph) the speed restriction cuts in if its a grey import, and it fires on two. This could be the cause. You remove this restrictin by bending back a little tab in the speedo, if this has been bent in the wrong direction your restriction will come in at lower speed.

Could be a short circuit somewhere, I hate these. All I can suggest if you eliminate the above two possibilities if to go over all the wiring looking for a cracked or broken wire, or a wire with some insulation rubbed off that could be shorting onto the frame.

Don't do anything until other people reply though, could be something else.

[EuropeanNC30R...]

Like Robby said, it's not going to be the can.

Get a multimeter across the battery terminals and check the voltage it's charging at when at 5000rpm, should be between 13.5 - 15.5V.

Could also be fueling, possibly caused by a weak vacuum in the fuel tap. It's fairly easy to convert the tap to gravity-fed if this is the problem (I had to do this recently). When the vacuum is weak the bike struggles to draw in enough fuel at higher speeds and when the fuel level is low.

Check the charging system first though.

[killa]

No I’m sure I did explain that it wasn’t the plugs, the mechanic came over and rev’d it to say 13-14 grand and then it was burbling and not sounding good.
He says it is because of the lack of back pressure cause by the very large can on the back.
The bike performs great at high speeds with a lot of revs.

What’s this about restriction?
The bike fukcing goes some and doesn’t stop at 112mph.
____________________
Cleverly disguised as a responsible adult.
Bike:- Yamaha TRX850 | Killas Biking History | Killas Gaming History | Killas autmotive history

[killa]

Actually thinking about it, after I got back last night and the guy had a look, we noticed a loose red wire (used to have an immobiliser) so we tape it up. Is it possible it was shorting on the frame before?
____________________
Cleverly disguised as a responsible adult.
Bike:- Yamaha TRX850 | Killas Biking History | Killas Gaming History | Killas autmotive history

[Claud 14.7 to 1]

[killa]

What i ment before is say, motorway driving is kool, constant speed.
Giving it a quick blip donw the road then slowing sometimes sounds like the fuel yes.
____________________
Cleverly disguised as a responsible adult.
Bike:- Yamaha TRX850 | Killas Biking History | Killas Gaming History | Killas autmotive history

[Stew]

[killa]

Thanks for all your help, is it going to cost me getting this tap in place?
____________________
Cleverly disguised as a responsible adult.
Bike:- Yamaha TRX850 | Killas Biking History | Killas Gaming History | Killas autmotive history

[Deano]

modifying your tap to a gravity fed one instead of one that is done by suction doesn't cost anything it's a simple case of taking the fuel tap apart and removing the spring and one of the diaphragms. Goto 400greybike.co.uk and on the main page their is a write up in clear detail about what you got to do.

[EuropeanNC30R...]

https://akhara.com/nc30/fueltapmod/index.html

It's free and you can tell your mates down the pub you've got a HRC spec fuel tap.