[i think xs 250 has beaten me]

frame "trimmed" flat track seat fitted (loosely) gotta cut tread-plate for battery and regulator and battery to sit on weld some nuts /.... hopefully frame sprayed up by end of the month

Jez

[xt500 non starter]

hey i love these things

take plug out to start with don't worry about starting untill you have a spark or you have no leg or foot left

clean block connecters from engine to loom clean the coils where they ground to frame then...

while looking directly at the contact breakers (dim the lights or late in the evening if outside) turn the engine over (easy now no plug) and see if you get a blue spark arc across the the breakers .

if none examine wiring (power)going into coil i think poss red/white if no power trace back to find out why (at this point try look for power while kicking over too) if you have power move forward checking each connection

good luck

Jez

[i think xs 250 has beaten me]

adjusted points gap to tad over max now have fat spark bike pulled well

now in bits ready for next stage ... electrics

...

[i think xs 250 has beaten me]

Hi

new coils from rex count

it feels retarded on the throttle but i have only balanced on rev counter 1 pot at a time need to put vac Guage's on

ill re time with fag paper and then strobe it

a whole new world of tricks is availble now its starting

the tip i broke was pilot mixture screw ...i found some more carb bodys in the basket case and the mixture screws were different (stepped rather than tapered) anyway i tried those in me bestest bodys and one broke ... i have yet to try airline up pilot holes to blow out

thanks for help

will keep it posted

Jez

[i think xs 250 has beaten me]

Makes things easy on yourself on the ignition. Set the points gap exactly the way it says in the manual. Then set the static timing the way it says here:

Now, once you get the thing idling on both cylinders (I have some thoughts about that, back to that in a minute) and after the static timing is set, with the points cover off, advance the timing slowly turning the points plate clockwise and the idle speed should increase. if it decreases, turn it the other way. When the idle speed is as fast as it gets, back it off a bit and tighten the plate. An engine with some wear will run better with a little bit more advance than stock. Based on your compression numbers, you have enough wear to benefit from this. After you set the timing this way, ride to make sure it is not pinging and check the plugs to make sure there is not too much heat. If there is, back the advance off a bit and ride again.

As for cleaning the carbs, if they are like those used on the XS400, the idle circuit passages can be finicky. Here's how I clean them (this is for BS34s, hopefully yours are similar). With the carbs off (you can leave them attached to each other) take carb cleaner and spray it through the air jet at the mouth of the carb. With the idle mixture screw in, but at the setting for running (try 3 turns out to start) a strong stream should spray out from the hole beneath the idle mixture screw. Turn the carb over and take the idle jet out and clean it and shoot carb cleaner up through where the jet was. You should have a strong stream out the same hole. Then screw the idle mixture screw in and lightly seat it. Spray the carb cleaner in the air jet while holding the carb butterfly open. You should see 3 strong streams coming out of 3 small holes just above where the butterfly rests. Turn the carb over and spray carb cleaner up the idle jet from below and you should see the same thing.

Spray until you can see the carb cleaner flowing in strong streams as noted above. If you can't see that, you may need to strip and boil the carbs (my preference...'cause it's cheap) or have them ultrasonically cleaned. If you can see the carb cleaner spraying out basically unimpeded, then the idle circuit is clean because you have cleaned it from both directions.

Hi thanks for input done all that a couple of weeks ago

the bit about advancing the timing plate may be handy

as above now idling and ticking over a treat need to balance carbs next and put check main jets and neddles as the carbs are made up now from random bits so to change one part at a time

NEED TO WORK OUT HOW TO REMOVE A BROKEN NEEDLE TIP (I BUST IT OFF YESTERDAY)

where's Drewpy Im interested in this plug gap anomaly

Jeremiah !

[i think xs 250 has beaten me]

it is the amount of "time" ie degrees angle over the circumference of the shaft the contacts are closed. This charges up the primary coil and when the points open, the electricity has built up so much in there that is inducts into the seconary and through the spark plug jumping the gap.

the more the coils are energised the fatter the spark.

VERY well put and now easily understandable

I wonder if it is connected to today's anomaly

XS 250 now starts well and ticks over well tick over ATM a little fast but sounds a lot better and it stays alive

it does try and respond to throttle but it ain't great but well .... Hey one thing at a time

Now the plugs that came with the bike(s) all six in fact were set to or near to what it says in the Haynes 0.7 mm

last night i thought i was getting close but all the plugs seemed to need constant attention apart from one when i examined it this morning it had a smaller gap (possibly dropped) i measured it at 0.4 mm set the others to that and hey presto ... intial prob's gone and bike starts and ticks over well..

Is Haynes wrong >>>>AGAIN.. or is there something more sinister ...

Possibly related to dwell ...gap set to smallest in Haynes book 'O' lies 0.3

thanks for the input Drew

look forward to your thoughts

Jez

[i think xs 250 has beaten me]

some weird shit tonight

started mixing up carbs

made up a new set slapped em on it was running a treat on the right cylinder

made up a new left no luck

made last left no luck right going well though

split carbs put right carb on left left ran fine put a left carb on left left ran fine ??? put these together no right

put a marked good right on right no right

got totaly mixed up now suspect we burning plugs out

but i think we are close

[i think xs 250 has beaten me]

Not quite, dwell is the time the points are closed,so its the opposite.

Ahh yes sorry when i researched "Dwell" i came away thinking it meant the time closed ... but the smaller the gap the less time closed = less power charged in the coil .. ?????

told you these carbs are finicky, are you really sure those tips have not broken off, can you see daylight with the carbs off and mix screw out?

Yes you did i did believe but cant see how to get them cleaner but it will be somewhere something ... The crux is three sets of carbs with the same or similar symptons . However we now know ignition is tip top .. Personaly when i have a doubt i keep going back.

I looked at mix screw through a jewelers eye piece had blunt end but we concluded that should be the case however ...

Ive only seen old ones

Ill take em off tonight and have a look see for daylight and get back on that one.

the only other thing is the float bowl has a fuel run and it did take me a while to ungunge it using compressed air, solvents etc.

drewps

bowl is deffo ok

but will check again

Thanks for replying

Jez

[i think xs 250 has beaten me]

Just some of the latest here

Dwell is Points Gap (new one on me) any way that's all good

I chucked a Mikuni vm34 (Jetted for a SR 500) on the left cylinder and with some fiddling it runs well and starts easily it will tick over very nice and not cut out miss or fart at all running one cylinder the plug looks nice too nice tan color

repeated the process on right cylinder all good runs ticks over nice looking plug

so its the CARBS

back too them stripped again blew out pilot holes and set floats (they were previously ultra-sonicly cleaned

back on same shit fires up now on two cylinders wont run for long it is missing and generally running very rough wont respond to throttle

what i have noticed is no matter where i put the mixture screws it makes no differance (I have even removed them) i cant work out where the problem could be

could it be between the float bowls and and main body there is a gasket there that looks very good the tips of the mixture screws look ok under scope

seriously considering getting some 42 mm copper pipe and fabricating a 2:1 manifold

Jez

[i think xs 250 has beaten me]

Ok out of intrest today (and the fact i cant seem to leaver the ****** alone

we slapped a mikuni vm34 round slide carb jetted for sr500 single on mr left cylinder no throttle cable just carb

choke fired after three seconds started to splutter & run on one cylinder choke off adjusting throttle stop i managed various degrees of succses and run on one cylinder for around 30 secs

didnt have time after to try right cylinder

....

carbs stripped again will rebuild next week off for the week end

Jez

[i think xs 250 has beaten me]

hmm had loads of XS250's do this with various causes

from the training I received in the early 80's I'll give you the diagnosis path

Compression check wet/dry

out of spec

Remove Cylinder head check valves for leakage

check bores pistons & rings for wear

in spec

adjust valve clearances to the correct values

set the dwell angle to 22.5 %

set the ignition timing (with strobe) to LF (left cylinder) RF (right cylinder)

Always start with the L/H cylinder when sat on the bike

Ignition timing & dwell are set at the same time you may set the dwell correct then adjust the timing which will then set the dwell to an incorrect value.... reset the dwell then recheck the timing keep doing this until you have the dwell and timing right

check the advance for both cylinders (between the | | marks)

adjust the mixture screws for a steady idle (some engines require the mixture screws to be set well away from the default 1.5 turns out)

check/adjust carb balance

Still running badly

check inlet manifolds for leakage the rubber o ring within the paper gasket can fail (you will see the 'gas track' across the paper section of the gasket)

if OK

check the diaphrams for splits. with a diaphram split this can give you a false reading when balancing the carbs so if you have a split you will have to do a re balance

if this doesn't fix it post up again

Ok right whats the ?? dwell ?? and whats the compression spec

Thanks for the input

[i think xs 250 has beaten me]

yeah 1 has cap other goes to petcock

whilst turning engine over with petcock in postion on or reserve petrol comes out prime just dumps fuel

so all ok and fuel cap open closed make no difference

i have even tried swapping cap and line about ... from one intake rubber t' other

re done compression test ... its not a very great tester its a cheapo am-tech i have borrowed and its hard to deduce the fast flickering needle but its hitting 125 psi as best i can see ...

Jez

[i think xs 250 has beaten me]

tried other carbs back to one cylinder (right) unable to get left firing so took carbs off cleaned left one blew out pilot jets and airways examined needles (tips look to be there) set them at three turns out from full in

now nothing will fire yes .. it has spark ...

i have restored bsa's that people pulled apart in the fiftys and left outside ... and a sr500 that lay in a hedge for twenty years ... this pile of **** defies all logic

[i think xs 250 has beaten me]

coils arrived ..... single wire wrong ones .... and i did tell the guy points in fact i ordered new points at the same time

[i think xs 250 has beaten me]

Hi

Bit more "un-frustrated" this morning

late last night after posting we did notice that when she tried to start on the right it was not as strong as when she tried to start on the left

we swapped coils and got same result so i tried another coil on right .. and now it does try and start on both cylinders

Current status tries to start on both cylinders

sound

possibly missing wont respond to throttle best its run for with out starter turning is about 5 secs

to start last night i had to remove air-box and block/restrict intakes once firing a bit i put air-boxes it the would continue to start ...choke on to start after a while it doesn't like it but still wont start ..

Carbs they have been ultra sonicily cleaned ... it made little or no difference

i have 2 other sets of carb's they have the same result ... same symptoms

...

I have put a new condenser on made no diff

Points I have gapped and timed using a light bulb timed to the first mark after LF ... I will say that i found this a bastard of a job as the timing wondered as re-tightening screws

but they seem to be on the mark now

I am thinking of the fag paper method but the hassle last time to get them spot on is putting me off

atu bob weights seem too be free

TODAY i will try

putting old condenser back on

some original exhausts

and brand new coils if they arrive in the post

Jez

[i think xs 250 has beaten me]

Ohh forgot

compression tested 100psi

inlet and outlets done set...

[i think xs 250 has beaten me]

Hi

I am very frustrated but i do see the funny side of this ...

well i have built rebuilt a few bikes ever but this f****** is taken me to hell well two of em now cos i bought another

will not run proper nor will the other

will start on one cylinder then other wont run ...

ahh you say .... no I say cos it could start on the opposite then the one that was running previously wont run

so far checked points gap good timed and retimed and some more then fitten new conatcts timed timed again

coils tried loads of different coils

new condeser

so i figured it the engine

so i buy another basket case xs250

swap engine

same thing

contacts timed retimed take off check advance all good

time retime check time a again

Carbs been to cleaned with ultra sound

have two other sets of carbs that do the same thing

go figure

as i type son is changing the exhaust system

with air filters on it will not start at all

take filters off and block pipes and she makes an effort ....

thats the only significent data i can present

HAS any One please got any ideas at all

Jez

going Mad

[Yamaha xs250]

Carbs are very picky on the xs's. they may LOOk clean, but in honesty, they need ultra sonic clesaning. "Mervin the mod" on this forum can do them. there are lots of small orificies, i cleaned mine but still ended up sending them away to be ultrasonically cleaned.

You can get Keyster carb kits from NRP in Manchester if you want to overhall your carbs and replace the jets etc.

what about single carb conversions is that done I have a few various old style VM mikunis lying around ? and a host of jets

[Yamaha xs250]

Sorry yes no spark to begin with ... but got that sorted the wiring was all bodged ... but it struggled to start since then ... we have retimed the points which were out sligtly

but engine still runs poorly and will not rev it will not start without priming the cylinders with petrol

i have checked the carbs they look very clean and the diaphrams look good

I am a bit lost now i suspect lack of fuel but logicaly it should get there as the carbs look good will strip cabs next I suppose

regards Jez

[Yamaha xs250]

Hi set points they were out but it has made no differeance

checked carb all looks spotless almost as if been cleaned before

diaphrams look good

good blue spark at plug

so bike starts with time and effort but not without a petrol prime down cylinders once started struggles to keep going and will not rev

i am a bit lost now .... not sure what to try next has anyone any ideas ...

Jez

[Yamaha xs250]

Hi yeah thanks all under stood the wiring around the points coils and power were all wrong and (fiddled with)

i have put that all right and she starts but runs very poorly and will not rev am now researching how to set the points in relation to tdc

gonna order a condeser and clean carbs

I have one question I presume there will be some tdc marks on generator flywheel

is flywheel wet or dry do i need to drop the oil?

[Yamaha xs250]

get a battery!

check fuses by removing and cleaning the glass fuses.

no power as such across the points its a ground for the coils.

fuses seems all good every thing else works ?

Thanks for reply i have a few questions i am very good in all mechs but tend to get lost with ignition timing and have learnt since electronic stuff so points are a mystery to me any help would be great

do the points draw there power from the battery or the alternator/generator

how do i test that power is getting to the points and does it need to be turning over to test this?

should i be able to see the points generate/release a spark? (atm cant see anything)

Jez

[Yamaha xs250]

just brought home a xs250 as a project for my son however has no spark whats the best way to establish if power is getting to the points

regards Jez

[hi]

Hi

just got a xs 250 for my son (Josh ) as a project

i myself run a sr500 in flattrack trim on the road but awaiting spry jobs

Jez