newbie in need of help

[bigpants]

Hi everyone , when i just logged in i realised that id actually joined in july 2011 but never posted or had cause to even look in. Now thats what you get with a Honda. Not like my last bike , a guzzi 1100 cafe racer with fuel injection. I was posting on the guzzi forum every week till i finally gave it up and went back to honda. But at last the gremlins are back . Im away from home now dogsitting and using a friends laptop so i wont post any pictures just yet but they say a picture paints a thousand words and one piccy of my bike would tell you all you need to know about me. My bikes are (ab)used hard every day of the year and run on a shoestring budget , i may need your help but my vtr depends on it !
Ok , here we go. Year 2000 bike , claimed 9500miles when i bought it in 2011 and no reason to doubt it. Always run very strong. Yesterday on the way back from work i was pushing quite hard , not revving high at all but working the throttle and box. After about 20 miles whilst powering on to overtake i thought it hesitated , then a few moments later it happened again. Now a day and 30 miles later its much worse. It starts and ticks over fine , low rpm ok but if i open the throttle to accelerate it starts to bog down , not sure its a misfire , more like it just doesnt fire , if i hold the throttle wide open it will just about keep going at whatever speed i was already doing but wont accelerate. Ive changed the plugs and checked for a blockage in the airbox.
If anyones got any clues please let me know.
Cheers (literally).

[darkember]

Hi there & welcome

From what u describe it could be fueling or electrical.

First I would check that all your vacuum pipes are secure. Then I would check your coil packs are reading correctly using a multimeter.

[bigpants]

OK , thanks darkember , ill run those ideas through the search facility .

[VTRDark]

if i hold the throttle wide open it will just about keep going at whatever speed i was already doing

The first thing I would do is check to see if each cylinder is sparking. Have gone through a load of water/heavy rain recently as this can easily get into the front plug area and give you misfires. But you say it starts and idles fine and bogs down when opening the throttle. So I'm thinking it's fuelling, maybe the petcock diaphragm.

(:-})

[lloydie]

my moneys on the petcock diaphragm or carb mount rubbers

[bigpants]

Yeah its definatly connected to the throttle in some way and not a random misfire , if it makes any difference i did change my cans a week ago. Do the symptoms fit with a broken throttle position sensor , i only ask cos my guzzi used to eat them every few thousand miles.

[sirch345]

Welcome back B/P

Chris.

[Wicky]

my moneys on the petcock diaphragm or carb mount rubbers

+1 with Lloydie and petcock fueling problem or air leak in the intake or exhaust system.

[bigpants]

Ok thanks for that , ill do some research here about how to check for this.

[bigpants]

update. ok ive taken the tank off and split the vacuum pipe at its midway join , gave it a suck and seem to be able to hold a vacuum fine. buggeration , i was hoping it was that. whats next on the list ?

[bigpants]

update 2. just disconnected the tps and went for a ride , no difference so not that. fresh petrol - not that. however if i ride holding the choke out it is quite a bit better. basically if i ride at low revs its fine , if i accelerate slowly around low revs its fine , but if i try to accelerate normally it stutters and bogs , if i go up hill it does it and if i accelerate down hill its better. with the choke on there is a bit of surging , bogs , clears , bogs sort of thing and feels like it may even clear if i was ruthless with it. feels more fuel than electrical but then nowadays theres a big crossover of technology.

[darkember]

Ok from your last post you have opened a can of worms/possibilities. Are you able to find out if you machine is standard setup. Things to look for are stock filter, aftermarket cans, any carb staging done ie: different jets ect. If you are able to find this out then you will be able to get back to a stock setup to get a bench mark.

[bigpants]

well no i dont know internaly whats been altered , the filter looks stock ie a red fluted square thing, but its funny you should ask . a week before the problems started i fitted a pair of cut down stubby silencers in place of the blue flame jobbies. i cant see how they would effect things but heh what do i know ? also for the first week all ran fine. tomorrow im gonna get the tank off and check the fuel flow to both carbs . i dont have any reason to believe its one cylinder rather than both but it cant hurt to check . it still doesnt seem to pop , fart or backfire so im still thinking fuel flow.

[darkember]

Mentioning that these bikes don't like short cans so I've been told.

[VTRDark]

Red fluted (not sure what you mean by fluted) square thing sounds like a BMC filter to me. Does it have the triangular sections in the corners built into the filter. If you have just put some stubby cans on then this is where your issue is. The carbs will need to be jetted to suit. You will need to strip the carbs down and see what's in there to begin with. If you have a BMC filter then there is a good chance that the carbs have already been fiddled with and have had a jet kit installed already in which case you will have adjustable needles. Have a read through the carb tuning guide in my signature and it will give you an idea as to what to adjust.

(:-})