Date: 29-03-24  Time: 02:22 am

Author Topic: Idling trouble  (Read 7269 times)

jackson1995

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Idling trouble
« on: 18 January 2016, 11:07:52 pm »
Hi guys,

Got a probably with my bike, when idling the two ride side(3/4)  cylinders are not running , once riding about 2500rpm it fires on all 4 ,
Things I've checked...
Spark , yes
Fuel , yes
Throttle cable slack
Air filter
Coils
Throttle position sensor
Starter diode
Pickups
Kill switches
Side stand
Float bowl fuel level
Butterfly's
Vacuum balancing
New plugs
New caps
Carbs have been apart
Diaframs are good,

So saying all that any ideas? I'm stumped haha
You can literally sit at a red light and pull the lead of the plug and bo change to idle.

Any more ideas will help!
Thanks guys
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unfazed

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Re: Idling trouble
« Reply #1 on: 18 January 2016, 11:55:56 pm »
Do you park it on the side stand all the time and has it been idle for a while?

Fazerider

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Re: Idling trouble
« Reply #2 on: 19 January 2016, 10:34:26 am »
Have you checked for low compression?

jackson1995

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Re: Idling trouble
« Reply #3 on: 20 January 2016, 01:11:36 pm »
I leave it on its side stand over night , but it's the two (sitting on the bike) right side cyclinders... 3 is mostly firing , 4 will not fire on idle , this morning ( ice on the bike ) no choke started on the button (3 cylinders) put on the choke held at 2000rpm and it was firing on all 4 , took choke off and back to three/two , compression check showed
(Left to right ) 1.70psi 2.80psi 3.nothing at all 4.100psi
Looking at the 600 manual I have , they're no where near spec (217) but not sure what 400 spec is?
Put a cyclinders leak tester on it..
1.10%leak  2.10%leak  3.90%leak  4.80%leak

How can cyclinders 4 show more compression then any other but have such a big leak?!

Someone hand me a lighter.....
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Fazerider

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Re: Idling trouble
« Reply #4 on: 20 January 2016, 07:29:53 pm »

Don't worry too much about the absolute values being a long way off-spec... chances are the tester adaptor doesn't fit as deep into the plug hole and the extra space reduces the apparent compression. The differences between them is more important.
Valve clearances are probably the next thing to check since it looks like cylinder 3 is in trouble. If the leakage and compression results for cylinder 4 are inconsistent that may be due to a sticky valve.

unfazed

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Re: Idling trouble
« Reply #5 on: 20 January 2016, 07:43:44 pm »
First part sounds like blocked pilot jets normally associated with bike which is left idle for months on the side stand.

Second Engine compression on the 400 is 217psi standard and anything under 174psi is consider low, but still works unless it is less than150psi which makes them difficult to start cold
compresion should be measured with the throttle open full.

Leak down does not look right at all and looks more like a sealing issue with the equipment  you are using. The leak down tester requires a very good seal as does the compression tester. Check the plug holes for debris which could cause sealing issues.

I have seen the odd issue with bad rings but most compression problems I have seen on the 400 is valves leaking, usually from burned exhaust valves.
« Last Edit: 20 January 2016, 08:17:43 pm by unfazed »

jackson1995

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Re: Idling trouble
« Reply #6 on: 21 January 2016, 02:07:13 am »
Thanks guys, the guy I bought the bike off was using it till I bought it (4months  :) ago) so hasn't been sitting around.
Your right , I don't think my testers were sitting properly in the plug holes because when I brought them out they was marked along the bottom edge.
I had time to whip of the rocker cover and check valves clearances, and there all pretty much within spec (1 or 2 are 1thou tight or so)

I have a lot of time to think about this on my commute to and from work haha , so I'm starting to think it's a jet hopefully ( I should've really checked when I was doing the float levels the other day)
That all I can think of, without going much further into pistons and ring which id rather not haha

I might try get some pictures / videos to show what I'm doing...

Unfortunately my dad managed to snap the 5 way carb fuel joining pipe when we had them out so I've ordered a new one from Japan so until that comes I don't want to pull the carbs and start playing with them because I've managed to keep it going with some tube an T peices and it's not leaking yet haha
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jackson1995

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Re: Idling trouble
« Reply #7 on: 24 January 2016, 06:58:23 pm »
ok well good news and bad news...


good news! had some time today so thought sod it ill take the carbs out and check the jets...
looked in the jets and 2 pretty much completely blocked! blow through and perfect! checked all the others and they was fine... ( out of interest i guess the idle jet is the long one with the holes in the side..?)
 so put it all back together about a hour or two ago... fired up and perfect! balanced the carbs and sorted! idled lovely revved up perfect..


now the bad news...
locked up the garage pulled away and miss fired... didn't take much noticed then it go worse and worse so pulled up in a petrol station to see if i didn't put something on or caught something and the vacuum pipe for cylinder three was not sealed to pushed the bolt in properly... went to start the bike and nothing! just turning over , checked for spark.. all good..
then it smelt flooded so put my headphones in and watched some videos on my phone went to start and nothing , twisted the throttle a little and bang on it come but only on 3 with one not firing at all and wouldn't rev up... then looked underneath and fuel poring out the overflow from the air box! anyway managed to get it back to the garage (very slowly) and quickly pulled the plugs and no.4 is dripping wet so now the new problem...


.Stuck float? i was adjusting the levels again to day and all was perfect! ( read they shoudl be 4mm over the float bowl seam??) so guess that or what?
.Also when i pulled all the plugs they are all running rich (black) i set the pilot screw on the bottom to two turns out but when i bought the bike they was 3? it seems to run fine when it is but was jsut wondering is screwing in or out making it richer or leaner...?


so now im sitting in the office at work waiting to be picked up and ill get a boring train into work tomorrow and pull the carbs again...
« Last Edit: 24 January 2016, 07:05:58 pm by jackson1995 »
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unfazed

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Re: Idling trouble
« Reply #8 on: 24 January 2016, 08:51:11 pm »
What make of carbs are on your bike Kehin or Mikuni?

They should be Kehin CVK, but some people change them for the Mikunis from the 600 and are very difficult to set up correctly, the assumption bigger is better is not always the case

If Kehin then the pilot screw should be 2.5 turns out from full in.

A rule of thumb with carburetors is: If the pilot screw is at the engine side of the carburetor then screwing the pilot screw out makes the mixture richer if it is on the air box side of the carburetor then screwing the pilot screw out makes the mixture leaner.

« Last Edit: 24 January 2016, 09:03:31 pm by unfazed »

jackson1995

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Re: Idling trouble
« Reply #9 on: 24 January 2016, 08:58:37 pm »
They are Kehin
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unfazed

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Re: Idling trouble
« Reply #10 on: 24 January 2016, 09:03:55 pm »
They are Kehin

Just modified my last post.

Here it is again.

They should be Kehin CVK, but some people change them for the Mikunis from the 600 and are very difficult to set up correctly, the assumption bigger is better is not always the case

If Kehin then the pilot screw should be 2.5 turns out from full in.

A rule of thumb with carburetors is: If the pilot screw is at the engine side of the carburetor then screwing the pilot screw out makes the mixture richer if it is on the air box side of the carburetor then screwing the pilot screw out makes the mixture leaner.
« Last Edit: 24 January 2016, 09:07:44 pm by unfazed »

jackson1995

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Re: Idling trouble
« Reply #11 on: 24 January 2016, 09:10:00 pm »
Thanks , but then I've only got them 2 turns out and it's still too rich (they're on the engine side) I think I'll sort this sticking float then ride around and check again , just wanna get this thinking running right now haha
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unfazed

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Re: Idling trouble
« Reply #12 on: 24 January 2016, 09:20:31 pm »
Could be a blocked pilot air jet or choke stuck on.

Did you reverse blow all the jets/orrifices including the air jets/orrifices when you were cleaning them?

jackson1995

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Re: Idling trouble
« Reply #13 on: 24 January 2016, 10:36:25 pm »
I just blow through the jets from the two carbs that wasn't working and down the holes they came from , when I take the carbs off I'll blow back
Don't think it's choke but I'll check that aswell
I'll let you know how I get on , thanks!
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His Dudeness

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Re: Idling trouble
« Reply #14 on: 26 January 2016, 03:15:17 pm »
I'd say carbs most likely too but another thing to check might be for spark. Do you leave your bike parked outside all the time? Anytime I've had those symptoms of low revs stutter and it's back to normal up the revs it's been from losing spark because of arcing through the plug caps. Water collects around plug 3 and 4 and gets under the cap which gives the electricity has an easier way to ground through the head so you lose spark at the plug. It's usually cylinder 3 and 4 that it happens on because of the way the bike sits on the side stand. You said replaced your caps with new ones so it's unlikely to be that but it's easily checked so no harm ruling it out.

jackson1995

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Re: Idling trouble
« Reply #15 on: 26 January 2016, 04:09:06 pm »
DONE IT!!


got into the garage yesterday , pulled the carb/jets/needles cleaned and back together on the bike turned on the fuel and left them for 10mins and it was fine then suddenly started overflowing again?!
pulled them all off checked the floats and all the levels was the same.. anyway i knocked them down a touched and refitted and perfect! running lovely ! gave it a good hour ride round town and its all perfect, gave it a quick oil change and its back better then when i bought it!


now ive just gotta wait for that new fuel line from japan...


thanks for everyones help and comments!  :faz :D
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unfazed

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Re: Idling trouble
« Reply #16 on: 26 January 2016, 06:05:14 pm »
What fuel line? I might have one

jackson1995

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Re: Idling trouble
« Reply #17 on: 26 January 2016, 08:25:28 pm »
It's a plastic 5 way junction , how do I add photos on here? I have ordered one
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jackson1995

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Re: Idling trouble
« Reply #18 on: 26 January 2016, 08:28:24 pm »
Go it. This is the pipe
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unfazed

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Re: Idling trouble
« Reply #19 on: 26 January 2016, 10:15:28 pm »
I have a full set of 400 carbs with a part of the choke housing on number 3 broken, but everything else is intact including that 5 way pipe.

You can have the full set for £60 incl postage




jackson1995

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Re: Idling trouble
« Reply #20 on: 27 January 2016, 11:58:07 am »
I can't cancel my order now since it's through Yamaha directly and paid but might still have them for spares! You don't happen to have the tps sensor aswell?
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Re: Idling trouble
« Reply #21 on: 27 January 2016, 02:18:40 pm »
Unfortunately not, I  sold it over a year ago to a fellow called Dan in Russia because he could not get one and had been looking for some time for one.

There are a few Suzuki and Kawasaki ones which will fit since they also use the same type Kehin carbs and are the TPS is also made by Kehin, but have shorter leads and you will need to make a few changes to the wiring to get it to fit. The lead on the 400 one is one of the longest I have come across on TPSs.

I have the info somewhere on my PC as to what one will fit, just need to find it.

If you want the carbs I can send them by courier and I will check the courier price and if I can get for less than what I think it will be, I will reduce the price accordingly.
The carbs have been stored dry, since they were taken off the bike just before I paid for the bike when I was buying it in Stoke on Trent. They were running, before they were removed, but I can open them and check everything is ok if necessary.
There was a problem starting it cold and when I pointed out the broken piece to the seller he replaced the carbs, but I kept the originals.  :)

jackson1995

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Re: Idling trouble
« Reply #22 on: 28 January 2016, 12:49:23 pm »
PM sent

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unfazed

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Re: Idling trouble
« Reply #23 on: 29 January 2016, 08:04:31 am »
PM sent back  :lol

unfazed

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Re: Idling trouble
« Reply #24 on: 31 January 2016, 10:09:37 am »
Alternative TPS for the Fazer 400, these may have a shorter lead which will need extending.

There may be others but I found these after a short search.

This site throws up a few new and used

http://www.frankmxparts.com/Throttle-Position-Sensor-TPS-/-Yamaha-WR400F (remove the plate and it is the same)
http://www.frankmxparts.com/Throttle-Position-Sensor-Keihin-FCR-MX-flatslide-carburetor-new

Picture shows 3 different model of bike including the Carburetor model R6 this looks a slightly different shape but the same fitting.

Occasionally like the Fazer 1000 replacement from a DR400 it works in reverse, but this is easily fixed by swapping 2 wires over.