Backfire - help / advice please!

[Minimoto]

Hi all. I just got a backfire up through No4 carb on my RVF. Anyone know what this could be a symptom of please??

Thanks.

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[Dynamohum]

Have you taken number 4 plug out to check it could be flooding that cylinder with float not seating overfilling with the airbox removed fuel will be seen flowing into the carb through the needle jet or out the double overflow pipes between the rear of the carbs ?
On a possibly unrelated matter to this problem i see you have fitted washers under the needles might be best to remove going by cammos guide it doesnt work on rvf carbs ?

[Minimoto]

Hi Dyna, I checked the plug, it looked ok. I've also checked the float heights and set them to 12.5mm as best I can (there must be some level of tolerance on this measurement..). The needles look to be seated ok as there was no fuel collecting behind the butterfly valves. I have taken out the additional washer, so I'm back to having just one under each needle.

I put the carbs back on last night, paying special attention to the rubbers. I also put a new vacuum hose on just in case, but couldn't get the bike to start. I think my battery might not have enough punch anymore. There's a spark, but the turnover speed is low...

Will try again tonight after a days charging and see how it goes.

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[Minimoto]

Wet plugs by the looks of it. Will give them a blast with the blow torch and give it a go later. Pretty sure it'll run then as it was firing on the dry test plug I put in one of the cylinders.

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[Dynamohum]

How did you get on with washers removed fully charged battery and clean plugs ?
A good battery is esential and the plugs dont just foul on the tips down the inside of the ceramic part of the central electrode also a quick sand blast and airline usually restores them to new.

[Minimoto]

Hi Dyna, it looks like I've managed to create and also fix a number of issues!! I'd obviously fouled the plugs and even a blast with the blow torch didn't help much, as when I tested them against the engine casing the spark was weak or up the barrel of the plug. My old IY27s looked much better when tested than the er9eh I was running with so I've swapped the lot and set the gap to about 0.65mm.

I will get the er9's cleaned up properly though as I'm sure they're still good.

I did another complete overhaul of the carbs and took out the washers as you suggested, but also took off the inlet carb mounting rubbers, cleaned and greased them to try and eliminate any air leaks and also replaced the vacuum hose and checked/set floats to 12.5mm as best I could - my least favourite check to do. Also tried to balance the butterflies by eye/feeler gauge...

Fired the bike up about 1230 last night and it burst into life actually sounding really great and quite responsive to a few blips on the throttle - as much as I dared at that time in the morning!! Can't wait to get home and fire it up at a reasonable hour today. I'll post another video... but it's definately heading the right direction now. I will need to measure clearances as well I think as I can only ever remember having them serviced once in the time I had the bike on the road. Made in 94, bought in 99, ridden until 08/09, garaged until now!

:-)



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[Minimoto]

Oh - the battery is making a bit of a sizzling sound...

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[Dynamohum]

You need to get valve clearances checked before any carb syncing is done .
More concerning is the battery boiling sizzling is it an old battery or just of a car charger which gives a boost charge 4 or 5 amps bike batteries only need half an amp or so otherwise it damages them .have you a meter to check charging system could be a regulator failure pull the plug from it and check for green corrosion burning etc in the plug.
Theres a charging system check how to on the forum any fault in system can give running issues also.

[Minimoto]

How does this sound?? :-)

https://goo.gl/photos/ZbXT876wtccgHRw56

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[Dynamohum]

Hard to tell from vid but it does seem to be picking up ok and settling to a fairly steady idle without the revs hanging good.
Test will be under load on the road and see how it goes then for mot test.
Would still give the charging system a check before venturing too far if its an old battery thats been laid up best replacing with new after checking the system is in order as you said earlier battery is sizzling and that regulator looks old school.
You can download a guide from the documents section borrow or buy a meter if you dont already have one .