450 2004-2008 poor idling etc

Taffy · Jan 19, 2017

I have three 450s here that are 2004, 2007 and 2008. and the first two i've put together run poorly at idle/tickover, they backfire and stall. also glowing headers unless I put in quite a large PJ of 45-48.

It helped that I increased the valve clearance to reduce the valve timing but at the end of the day I'm going to have to do shedloads to sort this I reckon unless somebody recoignises the problem?

BTW, it could still be ignition, still be a worn carb, can still be......

any ideas to cut short this long haul appreciated.

Taffy

Palle · Jan 20, 2017

Wow. You are the pro!

Airleaks?

And ye, ignition. I saw some transparent plug, like a window to see the real spark color.

Tps, does go up when you set idle speed.

Swap carbs and see.

Can you tell that im just guessing?

Taffy · Jan 20, 2017

on one of them we have swopped the stator, flywheel, pick-up, coil, carb cleaned twice then swopped, changed exhaust, plug, then we stripped the engine, then we swopped the engine.

but I haven't taken it seriously yet!

Taffy

husabutt · Jan 20, 2017

Sounds like a broken exhaust valve spring, knackered exhaust valves or exhaust valves not seating properly.

Taffy · Jan 21, 2017

seats cut and new valves Eric

cheers

Taffy

Palle · Jan 21, 2017

Well. Maybe manufactured by an intern, on a monday. Bet he liked kawasaki better to.

Kawestonltd · Apr 16, 2019

Any resolution to this? I fear I'm suffering similar symptoms...

Taffy · Apr 17, 2019

Not that I recall. my memory is terrible now. what i would do now is try a smaller PAJ in the front face of the carb. go down to a 60 and see what happens.

the thing is, look at most of my posts and i don't get a reply and that is when i'm trying to give help or advice, so the idea that i was going to get any help when I asked for it was always going to be a 'no chance'.

to me, it had to be ignition advance but what to do? clearly, half the combustion was taking place outside the engine! the trouble is, that doesn't have to be lean, it can be 'delayed' and it can be rich burning late.

the pilot screw didn't make any difference.

Taffy

fe600racer · Apr 17, 2019

Hi Taffy

This is a hard one by the sounds of it.

Is it the 2004 and 2007 that are not good and the 2008 runs well? If I recall the 2004 has the dellorto?

I have seen this where the carb boots on the 07 and 08 have small splits behind the hose clamps....
But this did not happen on the dellorto boots.

The small o-ring in the mixture screw is worn out or gone.

Spark plug cap wire not connected properly but you still get a good spark because when testing you tend to push down cap.

Many years ago I saw a case where the throttle slide was put in backwards......I don't think you can do this on a kein or dellorto though.

Exhaust pipe with air leaks.....

Small things but can be hard to find .......

Let us know what happens....

Regards

Taffy · Apr 17, 2019

all of them were bad. all are 2004-2008n which means Kokosan and keihin. no hose splits, no o ring fractured or missing.

an air leak in the exhaust has never been a problem really, not unless a very rich mixture which some of the old dell orto carbs had!

Taffy

Kawestonltd · Apr 17, 2019

What would happen if air was leaking into the carb intake from between the carb and the intake funnel? Wouldn't that bypass the idle circuit, lean out my mixture, and cause my problem? I see there is an o-ring at that joint.

I ask because I squirted a quick burst of starting fluid at the intake side of the exhaust with the bike running on choke, and the revs went up. The starting fluid was getting into the carb somewhere there, and my intake boot was tight. I see there is a gasket between the carb and intake funnel.

Now I need to make a short Allen wrench to remove the intake funnel to investigate...

Also noticed a nice little puddle of fork oil under my left fork leg tonight. Seals next. This thing was NOT well loved.

tinwelp · Apr 18, 2019

Probably irrelevant, but maybe worth noting my experience on a KTM LC4 some years ago showing similar symptoms. All the tail-chasing finally stopped with the consideration that the carb was worn and a substantial volume of air could simply run around the slide (it had a Dellorto) giving a lean mixture when at idle or small throttle openings.

Replacing the carb was outside of my budget, so I bored out the carb, made and fitted a brass sleeve, then bored it to match the slide. Problem solved.

Cheers... Paul

Taffy · Apr 18, 2019

tinwelp said:
Probably irrelevant, but maybe worth noting my experience on a KTM LC4 some years ago showing similar symptoms. All the tail-chasing finally stopped with the consideration that the carb was worn and a substantial volume of air could simply run around the slide (it had a Dellorto) giving a lean mixture when at idle or small throttle openings.

Replacing the carb was outside of my budget, so I bored out the carb, made and fitted a brass sleeve, then bored it to match the slide. Problem solved.

Cheers... Paul

wow!

quality!

if you use a Pilot Air Screw, it sits higher than the plastic inlet trumpet (who's real name is the AIR FILTER ADAPTER or AFA) and literally lifts the AFA off the carb. but it isn't a problem with a normal PAJ.

the thing is, you should be able to jet the carb to compensate for a carb problem. every setting is achievable.

note what i would do (once more)

Taffy

fe600racer · Apr 18, 2019

Taffy

This is a hard one.....let us know when you work it out?

They all have the same problem....so how can that be.....what is common....kokosan has been good if it was sem then that could easily have been it on all bikes.....bad fuel can happen and that is a common factor?

Valve seals? Crankcase seals?.....oil getting in would do it as the fuel from idle could be overwhelmed by oil.....lean from oil not air? Plug readings using unleaded fuel hard but any signs of oil?

With all the work and checking you've done the only common factor is the fuel! I hate empting the tank and putting in fresh 98 ron only to find it is not the problem but it's the only common factor?

Kawestonltd · Apr 18, 2019

Thanks for all of the theories and suggestions. Didn't expect this much from resurrection of an old post.

I agree that the jetting could be tuned to compensate for a lean mixture caused by air getting in where it shouldn't. If it wasn't possible, nobody would install pod filters or velocity stacks on their carbs (for the street, obviously). But in the absence of extra jets kicking around, I'll spend some more time trying to seal up the leak. I've ordered the rubber ring between the intake funnel and carb, and will see how that goes. Didn't have that laying around either, so should have added some jets to the order!

I'm not understanding how a pilot air screw would hold the intake funnel off the carb, or why that would be acceptable or work, but if you've seen it you've seen it.

The ignition theory is interesting, but scary. I believe Taffy's videos on ignition timing are on a model older than mine, and do not apply to my 2006.

Taffy · Apr 19, 2019

Kawestonltd said:
I'm not understanding how a pilot air screw would hold the intake funnel off the carb, or why that would be acceptable or work, but if you've seen it you've seen it.

I'm on about the alloy air filter adapter and not the plastic ones. I reckon sudco get them made in the USA? they aren't from Japan and I don't think the English end has the mental capacity to wipe his own arse let alone make them so I gies they're made in the land of apple pie and fake news.

the PAS sits about 1-2mm proud of the carb and so the alloy AFA's can't sit down and crush the O ring you talk of. it might also be true of the factory plastic AFA but i can't recall now.

but this isn't a problem on the standard bike.

Taffy

Kawestonltd · Apr 19, 2019

Taffy said:
I'm on about the alloy air filter adapter and not the plastic ones. I reckon sudco get them made in the USA? they aren't from Japan and I don't think the English end has the mental capacity to wipe his own arse let alone make them so I gies they're made in the land of apple pie and fake news.

the PAS sits about 1-2mm proud of the carb and so the alloy AFA's can't sit down and crush the O ring you talk of. it might also be true of the factory plastic AFA but i can't recall now.

but this isn't a problem on the standard bike.

Taffy

Good. I've got a standard bike, so shouldn't be a problem. The rubber seal doesn't seem to be treated as a necessity based on the standard FCR MX exploded view not including it, rather it shows up when shopping adapters. Sudco's catalog even states "** Highly recommended for Off-Road and RAM Air applications." Not a must?

I reckon you're not sure where those poor adapters are made, but would be happy to take a swipe at the US. We're not perfect, but one of the best when we don't clamor after repeating Europe's mistakes.

tourist · Apr 19, 2019

I don’t have much faith in the theory that a worn-out carb can be compensated for with jetting. It seems to me that, say, a mechanically loose slide is conductive to chaotic airflow - it probably passes more air or less air from moment to moment as it shifts around.

There are many stories of regret over time wasted on a worn-out FCR carb on Thumpertalk.

It’s easy to control for this variable: Get a new and known-good carb. Swap the poorly idling bike’s jets into it. Put it in the poorly idling bike. Test.

Kawestonltd · Apr 19, 2019

I agree with Taffy saying "any setting is achievable." Within the range of jets seemingly available for the fcr carb, one could work around a wide range of air/fuel mixture problems. But it's time consuming at best, even with a good understanding and feel of the bike/carb combination. At worst, most people have a poor understanding of carburetion in general, let alone of their specific situation. Then it becomes frustrating and kind of hopeless. It would be fun to have the time to tinker and learn.

Taffy · Apr 20, 2019

your forgetting that it is a 450 problem and not a 550 or 650 problem. that means what changes? no idea! we swopped carbs once, still the same, then we swopped heads = still the same. we then realised 'we' (the royal 'we') didn't write down what belonged on what and when and where. I was pretty pissed off about it.

That's another reason I don't have a workshop. you're conducting a test by guiding your mechanic, you discuss everything with him in which he's happy to lean back against the wall and say 'yeh' (and like whatever you say, i get paid either way) and at the end of it he hasn't made notes of anything he's done. "Can't be arsed!" cost of tests running into the hundreds.

Taffy

Search

Search

450 2004-2008 poor idling etc

Taffy

Palle

Taffy

husabutt

Taffy

Palle

Kawestonltd

Taffy

fe600racer

Taffy

Kawestonltd

tinwelp

Taffy

fe600racer

Kawestonltd

Taffy

Kawestonltd

tourist

Kawestonltd

Taffy

Similar threads

Register CTA

Recent Discussions