VFR 400 bogs down at 6k

[majormadass]

hey guys, my bike recently has started to bog down at about 6k, as if its sucking in air, and struggles a bit to get past, but once its passed 6-7k its fine again, seems to only do it in 3rd/4th gear i think, and beginning to wonder if its spark plugs or carbs? and my bro said some black smoke, he thinks its an air problem, just wondering if you can shed some light on this little problem? something to do while weather aint to good :) thanks!

[porndoguk]

what size main jets you running on?

[Cammo]

Check to see whether the rubber flap in front of the airbox snorkel is there.

[majormadass]

rubber flap is there mate :) the jets are standard i think, although i think my brother said 1 is slightly different unsure why? just trying to sort this little problem out, apparently it can be common on the vfr400 just jope people can help ! few people suggested cleaning carbs etc, check air filter and oil filter too!

[Cammo]

the jets are standard i think, although i think my brother said 1 is slightly different unsure why?

Until you have a look inside the carbs yourself you can never be sure of what's in there. These bikes have usually had at least a few owners, you never know how much a previous owner has screwed around with it!

The flat spot will probably be fuelling related. Clean the carbs and all jets, make sure the air filter is clean. If that doesn't help then raise the carb needles. That will usually sort these types of problems.

[majormadass]

ive cleaned the carbs and stuff before, and sorted pilot screw etc out with my bro, and that sorted a problem similar to this, my brother also said he thinks its air related and said i should get a new air filter and oil filter and clean the carbs and check spark plugs, hes a level 3 qualified mechanic bike he studied at stockport college, so he knows a fair bit, but i have to find out other peoples opinions incase they know for sure to confirm his thoughts, so hoping you can help :D

[uber pikey]

No offence but there is no better way to know your bike than to work on it yourself, bare in mind these bikes are 20 year old now and will usually supply you with grins and frowns.
Follow this thread done by cammo and you cant go wrong viewtopic.php?f=24&t=14524 I did and the bike runs a dream. It's worth doing the easy things before throwing money at them as I know plugs are expensive.

Curt.

[majormadass]

Thanks Curt, i will do mate :) i've mainly worked on the bike with my brother watching over me so i don't do nothing wrong, he makes me learn lol :) had a similar problem to this before it was sucking in air, so took carbs out, cleaned jets and carbs etc, made sure back on proper, and was working fine :) just hope can get it going again, like i said ive spent loads on it lately just want it running smoothly :) the only thing it needs is a new engine and frame pretty much and its been fully rebuilt lol!