my VTR appears to be back firing,

[Taz69]

Hi all,

I have got her booked in for MOT tomorrow, going to have a look at the hoses and plugs today, just in case.
Any idea on the size of hose I need to replace the vacuum on the carbs etc, is it 5mm?
Thanks for all the advice.

Mark

[Taz69]

Just got in from the MOT station, all passed,
However popping still there, the guy at Unity Road MOT, very helpful, reckons its only firing on 1 cylinder But to me it seems like its firing on both, very confused.

Mark

[AMCQ46]

the temeperature of the pipes will tell you if one is not working...............DONT just touch it with your hands, I dont wnat to be responsible for the subsequent injuries.

if you have a thermocouple that will be best, but the other option is to do it in the first min after start up [from cold obviously] and spit on them or drip water on them. how fast it boils off will tell you how hot.

if both same temp then both runimg, if one is colder then it is not running clean.



usual health & safety rules and disclaimers apply, I did not tell you to hold onto a red hot exhaust

[Taz69]

the temeperature of the pipes will tell you if one is not working...............DONT just touch it with your hands, I dont wnat to be responsible for the subsequent injuries.

if you have a thermocouple that will be best, but the other option is to do it in the first min after start up [from cold obviously] and spit on them or drip water on them. how fast it boils off will tell you how hot.

if both same temp then both runimg, if one is colder then it is not running clean.



usual health & safety rules and disclaimers apply, I did not tell you to hold onto a red hot exhaust

thanks for the reply mate, I have put her in the garage now so I will check in a bit when she is cold,

The spark plugs were replaced a couple of years ago and due to illness and work I bet she has not done more than 1500 miles since, lol
Mark

[Taz69]

Right, I just went and started her up and put my hands on the front and back down pipes and both are getting hot.

I know that means surely its firing on both cyclinders!

[tony.mon]

Yes, it is.

Lots of possibilities, but most likely to be fuel related after being laid up.

[Taz69]

Ok chap, looks like I'll strip off the tank again, check vacuum lines, bowls etc.

Thanks

[Taz69]

Hi all,

I have removed the tank, air filter and housing, however the breather hose going from the airbox to the rear cylinder seems very loose, literally I can just pull it off the cylinder without compressing the clip thats on there, could this cause the issue?

I am not sure how critical the breather hoses are on this.

Thanks

[benny hedges]

if the breathers are loose and drawing in air, they will artificially weaken the mix as the air is sucked in under the filter.... a weak mixture will make the bike pop & fart like a good un.
might be worth popping the clip off and giving it a good squeeze to tighten it up then whiz it back on.
are the pipes decayed at all???? if so replace them with new.

[Taz69]

Benny thanks for the advice, I will sort through the pipes, the vacuum hose from the petcock to the cylinder is splitting on the inner core when I removed it from the petcock, so I'll replace that one.

I will replace or sort out the clip so the breather is tight.

I have actually got the carbtune balancer here now, I also purchased a take off valve connector thats on the rear cylinder as I seen on the how-to balance thread that it can be used and left in, so I managed to get one from Fowlers today, but its too small for the hoses from the carbtune and I am having trouble finding 4mm vacuum hose anywhere in Bristol. So it leaves me having to find an adaptor to go from 4mm to 5/6mm so I can hook the balancer up.

Mark

[benny hedges]

the split vac tube is more than likely the cause of your trouble.

try halfords - if they havent got any just go to a local scrapyard & get robbing.
if it is too small, dip it in a cup of hot water to soften it a bit.

[Taz69]

Even if its only the tube going from the cylinder to the petcock? never thought of that one,

[benny hedges]

yeh that would defo make it backfire and pop and fart on over run and be down on power as it's drawing fresh air into the cylinder after the carb and also probably not opening the fuel shut-off diaphragm in the tap proper and starving it a bit.
get it mended!

[Taz69]

Cheers Benny,

I will get it sorted, balance the carbs, replace the plugs and hopefully she will be fine.

[AMCQ46]

agree with benny, if the vac hose is perished, that is 99% sure to be the root cause of the popping & banging