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TOPIC: IT 250 not starting

IT 250 not starting 15 Apr 2018 00:24 #1

  • webfluid
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engine rebuilt, carb rebuilt, have spark ..... a better spark since changing ignition coil but bike will not fire.
i recently Altered the loom by removing front brake switch and associated wiring. had the bike running and then tidied up loom position.
initially started looking at timing and unless i am misunderstanding the manual everything aligns as it should.
i then moved onto kill
switch, it ran before have checked the switch with multimeter and it is working .so i have a spark have fuel and air.
not totally convinced i have re arranged the wiring properly since removing the brake switch from lever and loom only for the reason it did run briefly before i meddled with it.

there are a 100 questions i could ask every kick over fills the engine with another jet of fuel which drains off into exhaust and fouls the plug.

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IT 250 not starting 15 Apr 2018 01:33 #2

  • RT325
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I wonder if it's just got a belly full of fuel now & needs a tow down the road, or drain carb & leave fuel off then push it around the yard with plug out but leave the stator wires unplugged just incase of fuel igniting. If it's got spark then ya most of the way there. Timing is controlled by the flywheel key pretty much so long as the key is still in one piece & not shorn/sheared? off when it last ran. If it 'is' well flooded then full throttle while kicking is required till it lights up [& no choke-if it 'is' well flooded]. But in saying 'that', if you 'do' push it around & drain the carb & it won't fire, then you might then need choke for a couple of kicks with throttle closed or choke doesn't work. Talking timing again sorry--you say all the marks line up but if the key is broken then the crank could be 'anywhere', but marks might still align. Mind you, if you've measured the piston btdc at whatever it is--guessing 2 or 3mm btdc & the marks align then i give up as all that is ok to go. Sorry that makes hard reading--think i've been here before. One more though--if there's heaps of fuel in the pipe it could be finding its way back into the cylinder if it happened to stop spinning at bdc with exhaust port open. Just looked at images & pipe goes downhill out of the port so that won't happen, or not easily.

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IT 250 not starting 15 Apr 2018 08:04 #3

  • webfluid
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i can confirm the exhaust bend was full of fuel, so i have drained that off, and i did have a leaking petcock, so i have now changed that. The timing has confused me as i convinced myself it is
controlled by the crank key but i have spent a good few times checking it all the same.
it was back firing on kicking it over when i initially put engine back in, but since checking timing it has stopped back firing and now just doesn’t start and fouls plug within 2 kicks

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IT 250 not starting 15 Apr 2018 08:17 #4

  • MarkT
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I'm with RT325... leaky petcock and pipe bend full of fuel means bottom end is likely still full of fuel... need to clear it out.

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1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250

IT 250 not starting 15 Apr 2018 08:24 #5

  • webfluid
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do you mean below the pistoni in crank area or in gearbox?well this something i didn’t even consider, that the petcock may have been leaking continuously the plug seems to be at permanently wet unless it starts.1st go
so if i take plug out put in gear and push it about that will get fuel out of crank area?

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Last Edit: by webfluid.

IT 250 not starting 15 Apr 2018 09:44 #6

  • Mothersbaugh
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webfluid wrote: so if i take plug out put in gear and push it about that will get fuel out of crank area?


No, it will not. What he is saying is that the lower crankcase, beneath the piston, is full of raw gas. You can take the jug off and siphon it out, or take it off and wait for it to evaporate. But make sure you have the petcock problem fixed first. Also, you probably have a bad float valve or the float level is incorrectly set, as even with a bad petcock, the float valve should shut off the flow of fuel to the carb bowl. Check that was well.

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IT 250 not starting 15 Apr 2018 11:03 #7

  • MarkT
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RT325's method of a tow/push start is what I would do... Drain the carb and keep petcock off of course, no need to add even more fuel! If it's really, really badly flooded plug out and pipe off (MAKE SURE you don't have any chance of spark with plug out or don't try this!) and a good tow/push in gear with throttle wide open should clear most of it. Pipe on and plug back in and tow/push until she fires. Then petcock on and you should be good.

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1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250

IT 250 not starting 15 Apr 2018 11:07 #8

  • webfluid
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have been in contact with guy who cleaned and set the carb up and he said take fuel pipe off and blow carb cleaner through it, that did stop fuel coming out carb breather , but has told me do not adjust float level as it is set right,

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IT 250 not starting 15 Apr 2018 13:37 #9

  • webfluid
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i like the sound of this and will give it a try would love it to be this simple and i think you have all again got me trying something i hadn’t thought of, which is good. it sort of makes sense leaking petcock has been dripping fuel into engine even when it’s parked up as level has gone down and it’s going somewhere .

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IT 250 not starting 15 Apr 2018 21:15 #10

  • RT325
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petcock [fuel tap down here but i'm learning lol] in theory shouldn't matter if it doesn't shut of 'if' the float valve in the carburetor is doing its job. I'd be looking there as well as the fuel tap. I remember on my kids JT1 in the '70's i fitted an automatic tap off a yamaha V50 scooter & avoided any possibility of accidental flooding. Is vacuum operated off the inlet, but that's getting extreme in this case.
Just thinking outside the square--no chance you've fitted the stator plate around half a turn, or third of a turn as think they're have 3 screws? but wouldn't be easy to do that. On my 465 motor i got a stator plate off ebay with a good stator source coil & it turned out to have a faulty trigger coil which had me thinking i'd lost the plot 'finally'. Would fire but too far out to run. Was no way of altering that & strobed it at kick start speed to see where it was firing. I compared the reading between old & new trigger coils & were a lot different but still wasn't sure as the don't measure very high anyway. In desperation i swapped the old trigger & never looked back--so another lesson learned. At work we had an xr500 single shock come in kicking back like a wild beast & harder than an old yamy360. Owner had broken the kick start shaft previous & it was going to happen again. Was the trigger coil causing it. Was a known fault so an easy fix in this case. I'm still not sure how all that works as can't see how you can get more resistance if the windings are shorting together & thought you'd get less, but would take 'more' to get a voltage rise sooner to cause kick back--advance. I'll leave it there as confusing myself.

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