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The TTR250 FAQ web pages -> TTR250 -> Repairs and maintenance -> 05 ttr250 intermittent miss.
Post Info TOPIC: 05 ttr250 intermittent miss.
Stickerking


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05 ttr250 intermittent miss.
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Ok, this thing is not responding to my advances.

Bike was left sitting for over a year, carby was the first focus of attention, needed ultrasonic cleaned etc and new diaphragm for the acc. Pump and other assorted o-rings, seals etc.

Accelerator pump is squirting.

Bear in mind I have tried another carb and the problem persists.

Bike is hard to start cold (valves come up within spec) and won’t start on choke.

When  I finally get it to fire up it idles and revs fine but still won’t take choke.

When riding it might go ok for 20seconds or 1 minute always Varys, then just off the bottom but not right off the bottom,it will miss on of on off etc then continue to run fine in the upper revs and higher speeds.

Eventually I coughs and dies under load and takes a bit to start , then runs fine for an undetermined amount of time before doing it again.

i have checked all electrical connections (wd 40 in there as well) checked ignition switch, side stand switch, kill switch, all come up fine.

Anyone got any ideas, coil?

i dont have a manual for the test values.



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ttboof


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Sounds like its worth checking the inlet stub 

 



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TTRfan


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Welcome to the forum!

As Les suggests, the inlet stub could be leaking - see here

Another thought is that the symptoms suggest the pilot jet might still be partially blocked. I have found that ultrasonic cleaning does not properly clean the tiny jet hole and you need to ream it with a bit of copper wire to make absolutely sure. 

More info here.

Brian



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Stickerking


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Thanks for the reply’s, the inlet stub was in fact torn away(discovered this a while back)I have put a hose clamp over the section and tested it off the bike, can’t get it to leak but it may be the problem regardless.
The pilot jet is clear.
The other carby test would have suggested it’s not in the carby I assume.



-- Edited by Stickerking on Sunday 1st of September 2019 09:56:21 PM

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ttboof


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If it's an electrical miss it should be a pretty definite cut out /in.  You have checked the switches not a case of good switch that needs adjusting eg stand moving around. 

Mine  was terrible to start until I went one size up on the pilot jet great improvement 

They are really hard to get clean 

If it's an air leak or fuel may feel more like a hesitation (softer cut out/in) 

Have never come across a bad coil but a possibility it's on its way out. 

 

The kill switch can test OK but if it's full of dust /mud it can cause some grief. 

Doesn't sound like a tank vent usually takes a while to die usually under load 

Is the idle air mixture set OK approx 1.1/2 turns out if not may back up the pilot jet being dodgy.

Haven't seen any long term successful repairs on the inlet stub the inlet pulses give it quite a hiding   I have a spare Chinese one on the shelf but haven't needed it as yet looks OK

Just a few thoughts before I head out in mine for the day I have the week off work. 

Good luck hope you find the culprit soon 

 

 



-- Edited by ttboof on Sunday 1st of September 2019 10:31:48 PM

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Stickerking


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Ordered an inlet stub, hopefully that’s the culprit.
Will update.

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mossproof


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Presume you haven't got a mouse nesting in the airbox and the in-tank fuel filter is clear?
Do you have another bike to check the carb on, or was the 2nd carb just a spare on the shelf?
Bit of a head scratcher! Good luck.

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ttboof


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The in tank filter is a good call 

 



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TTRfan


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Yep - good call Simon.

It's worth checking you have a good flow of fuel. Put a decent size rag or container under the carb float bowl and open the drain valve and check that you get a good continuous flow of fuel AFTER the float bowl has dumped its initial load (quite a lot!) of fuel.

Brian



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Stickerking


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Have checked fuel flow, if the stub don’t help I will hook up carb to tank and check flow plus the float level again.
Have already checked in tank filter, all good as is the tank cap vent.

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Stickerking


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Well the inlet stub did little to help.

Took an eternity to start and once going it would idle nicely.

when I was trying to start would not take choke, just fast idle for a second then die.

It seems it only misses is when I give it a high load situation, lots of throttle at a low rev and it sputters.

The carby I borrowed I suspect may have the same problem as my bike as I have learned won’t start and has been stored

for many months like mine.

This thing has really got me stumped.



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mossproof


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It sounds like you've answered your own question if the other carb is from a bike that has been stored too, and won't start either!!!
They can be VERY temperamental and take a lot of thorough cleaning after a layover without being drained.

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Stickerking


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I would have thought the ultrasonic clean would have fixed my carb.
The pilot looks clear, everything is spotless, new acc. Pump diaphragm new o-rings etc.
Was hoping the symptoms would be a clue for those who had similar problems.
The only part I haven’t changed is the float needle, but it’s not overflowing.

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TTRfan


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Stickerking wrote:

The pilot looks clear, 

They may look clear but always ream the pilot with copper wire to make absolutely sure wink



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mossproof


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Filter behind the float valve clear?

ttr250.activeboard.com/t45797183/petrol-filter-above-float-valve-seatneedle-float-valve-filte/

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Stickerking


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Yes had the float valve brass housing out, all clear, time to dive back in, will run a wire thru pilot and double check the whole carb again.


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