Hesitant revs below 3,000 RPM when hot.

[Bradders]

Rode my bike today without the air filter as suggested by Northy and seems to of solved the problem. Will try agaiin tomorrow and if ok will buy a new air filter. Also changed the gauze ( Scourer pad ) as it was a bit mucky. Thanks for the suggestions.

[K2-K6]

Hopefully you'll find it's the same with a new filter installed now.

A friend with a 400 (years ago and new bike) had been riding to work in the rain, sunny on the way home but the bike just wouldn't run or rev at all once warm. Just about made a detour to the supplying dealer, bike chugging along at slow speed, they had a look at it,  opened the seat and took out his waterproof overtrousers,  at which point it ran fine again. Mostly blocked the filter box intake with the trousers 

Let us know how you get on Bradders.

[Bradders]

I will K2-K6. Is Dave Silvers the best place to get a new filter from?

[K2-K6]

Probably DS as I doubt you'd find local stock for that bike. Unless other owners have better direction to buy.

On second thoughts,  check Bike-bitz near you in Yately as he may be able to supply and it'd save you the postage charge from DS. If you go from Sandhurst to Yately,  when you reach the main road there he's on the right just next to that junction.

[Bradders]

Thanks very much K2-K6. I didn’t even know they were there! Will give them a try.

[Northy]

Oh just had other thought (like you do ).
It could be the O rings on the main jets are  worn or not sealing properly , therefore making it run rich . So if the new air filter doesn't cure it that would be my next port of call.
Does mean the carbs will have come off but its not bad job if know the correct procedure.

However your issue is at low revs so suspect not ....  (make up mind  Northy! ......I talk to myself lot !)  

[Bradders]

Morning all. Some of you may recall my original post some time ago. Still having problems with rough running below about 3,500 rpm when the engine is hot, in fact it’s getting worse. Have adjusted mixture screws with the help of my mechanic so think they are probably about right. Changed plugs, air filter as well. Wondered if anyone had any more suggestions I could try. The problem is a lot worse when the engine is hot, almost to the point that it feels like the engine is going to stall when pulling away. It’s driving me nuts!

[Nurse Julie]

In very, very hot weather like some of the days recently, my 400/4 behaves exactly the same and mine is set up 100% spot on. As soon as the air temp drops, she's perfect again.

[Bradders]

Hi Julie. It seems to do it when the weather is cooler as well. Rode it to work at 5-30 in the morning when it was nice and cool but was still the same.

[Nurse Julie]

What are your air/ fuel screws set at?.

[Bradders]

I’m not 100 per cent sure Julie as my mechanic set them up last week. I know he started off at 2 turns out.

[Nurse Julie]

You need to check Bradders, he may have started a 2 turns out but did he end up at 2 turns out or more or less? Correct Air/ fuel mix will make a huge difference to how the bike runs.

[Bradders]

Ok thanks Julie. Will have another look.

[JezzaPeach]

When you first start it have you tried feeling the header pipes to see if they warm up evenly?

[Bradders]

When you first start it have you tried feeling the header pipes to see if they warm up evenly?

I haven’t tried that. Would that indicate if the leads or coils were suspect?