Mayday: 4-stroke problems

[Rupe]

Probably because you're $-stroke is so much louder ? Guess that does'nt quite answer the question why the 250 t-strokes are'nt alllowed to run with the 250 f-strokes , they have to go with the 450's , likewise the 125 t-strokes have to run with the 250 $-strokes ...am I the only one who get's annoyed by this ?? Where's the logic .......

What are you getting annoyed about??? pretty sure there was a thread about 250 4t's and 2t's in the same mx class over here have a search. Not sure what the $-stroke is about either, do all my own work on bikes and so far the 4t is working out cheaper than my 2t by a small margin. Both 4t's and 2t's have there own advantages, don't get to hung up on it, ride what you want. And help the guy out who asked for it, not bitch and moan.

[laserracer]

Are you sure the exhaust header is seating properly ? could be an exhaust leak..might pay to take off the header again and compare it with your old one ..seems funny it only started doing it when you changed exhausts

[2fitty]

Are you sure the exhaust header is seating properly ? could be an exhaust leak..might pay to take off the header again and compare it with your old one ..seems funny it only started doing it when you changed exhausts

yeah pretty sure, but will double check. its exactly the same header but not all bent and cracked . no it was doing it before too , thats why i got the new header cos i found the crack in the old one and thought that mustve been the problem. but no, as long as its not losing any power and the misses isnt overtaking il tough it out.

[warewolf]

went for a skid in the weekend and its still backfiring, any ideas why?

It's not necessarily a problem. It's quite common on new road-registered bikes that are set up quite lean to meet the emissions regulations. It's worse with the exhaust port air injection systems, which works as the TT thread says, adds fresh oxygen to the exhaust pipe to help complete the burn. They also have the side effect of simply diluting the nasties with lots of clean atmosphere... sneaky way to reduce the parts-per-million of bad vs good!

Many people suddenly notice it when they fit a louder exhaust, which not only amplifies the sound of the popping but can make the idle mixture leaner which makes the popping worse.

If there is no actual problem, I wouldn't bother richening the idle circuit only to get rid of the popping. But if all you did was fit another similar exhaust, I would be checking you have fitted it well and don't have any air leaks (per laserracer), not just at the headers but at all the joins. If the old one was badly beaten you could have bent mounting brackets, which are stopping the new one from mating correctly.

[2fitty]

still having dramas with me bike, backfire popping has gone to a loud crakling and when i twist the throttle sometimes bogs down and almost stalls, can anyone reccomend a good mechanic or someone who knows what they are doing, pref in the eastern auck area to sort it out, before i completley screw it up myself.
cheers guys

[4stroke]

take it down to puke to mr motorcycles, scott411 on here they'lll sort it out.

[Rupe]

still having dramas with me bike, backfire popping has gone to a loud crakling and when i twist the throttle sometimes bogs down and almost stalls, can anyone reccomend a good mechanic or someone who knows what they are doing, pref in the eastern auck area to sort it out, before i completley screw it up myself.
cheers guys

Sounds like you have an air leak at the carb, either hot start, or carb boot thing. Take it to Mr moto's or Spectrum on the Shore.

[2fitty]

cheers guys, was hoping for someone a bit closer to home, and to have it sorted by this weekend, ah well. mite try mr motorcycles then

[CookMySock]

when you wind it on it splutters and farts then dies if you dont keep the power on, its also backifirng quite a bit on deceleration.

Normally that means "really lean mixture". What colour is the tailpipe?

Steve

[2fitty]

Normally that means "really lean mixture". What colour is the tailpipe?

Steve

sorry steve, dont know what you mean by the colour of the tailpipe, its got the original silencer, a new header pipe 10hrs old, new gaskets and a new used carb off the same model/year bike. had to buy a new carb after i tried to fix the last one myself and stuffed it, so am keen to leave it up to someone who actually knows what they are doing.

[SS90]

sorry steve, dont know what you mean by the colour of the tailpipe, its got the original silencer, a new header pipe 10hrs old, new gaskets and a new used carb off the same model/year bike. had to buy a new carb after i tried to fix the last one myself and stuffed it, so am keen to leave it up to someone who actually knows what they are doing.

I suggest you check your valve clearances, Actually, when was the last time you did that?

If your exhaust valve is tight, it will actually remain open slightly and cause a lean mixture, as will the inlet (if it is too tight) and cause backfiring out the carb (in this case)

I can't understand why none of the contributors has suggested this.

[2fitty]

had a mate check them about 12 hrs ago, he said they were fine. thanks for the info mate

[SS90]

had a mate check them about 12 hrs ago, he said they were fine. thanks for the info mate

I am surprised, given the problems you are having, and since you have swapped carbs, and it is still the same.

What about the valves leaking (possibly damaged due to over rev at some stage), is it hard to start when hot?, the symptoms you describe sound very much like a leaking valve.

If you are able, try to get it somewhere where you can have a "leak down" test done, it is a simple test, and will let you know what the condition of your top end is like.

[Reckless]

I'm Howick same as you 2fitty if you had a 2 stroke I'd fix it for you, sounds like valves to me, but I know fuck all about 4 strokes??

But if you want someone closer to Howick John in the service dept down At Botany Honda is very good! You will be paying retail through them but he will probably tell you what he thinks is wrong if you trailer it down there and start it for him.

OH shit I just thought of Barty as well at NAR. Barty5 on here, is workshop is in Newmarket, Newmarket auto repairs I'm pretty sure! He's a four stroke man! PM him he posted on page 1 this thread!

[2fitty]

I'm Howick same as you 2fitty if you had a 2 stroke I'd fix it for you, sounds like valves to me, but I know fuck all about 4 strokes??

But if you want someone closer to Howick John in the service dept down At Botany Honda is very good! You will be paying retail through them but he will probably tell you what he thinks is wrong if you trailer it down there and start it for him.

OH shit I just thought of Barty as well at NAR. Barty5 on here, is workshop is in Newmarket, Newmarket auto repairs I'm pretty sure! He's a four stroke man! PM him he posted on page 1 this thread!

Cheers reckless, now i know who to call when my misses 125 starts playing up, have been down to botany honda and he thought it was an air leak or running to lean, but its well due for a rebuild so ive been told and am not really in the position to be paying retail for it at the mo, have been talking to barty on here also ,so am hoping we can sort something out. good to see another howicken on here, let me know if you want to go for a ride sometime. usually just ride with my misses now that my other riding mate has moved back to the mainland.