Hi everyone

Been lurking in this fourm for a while and thought id ask for your expertise

I was recently riding slowly through my town when my dt suddenly died and ground to a halt, it has not seized. i tried to bump start to no avail, i got into my garage to find it has a spark and put my thumb over the plug hole to do a poor mans compresion test(im not sure what to look for here but i did feel a pulse of quite strong air).I recently had it serviced as i do with any new motorbike.

Unfortunately it was done by cowboys. who while messing with the loom (it is old and corrodied they told me) accidently dissconnect the PV then Didnt do up the front head lamp nuts and as i was riding away with a bike that wouldnt bite the light was also slipping down. eventually they fixed all the problems and im not sure if what has happened now has anything to do with them

anyway, when i turn the key theres no Zssst zsst from the PV and the stater motor just keeps turning. after a while of trying to start the exhaust will sound like a loud sneeze or a puff, im taking it to bits to see if somehow the power to the PV is comprimised. i just wanted to ask if you have any ideas, The plug is in great condition with a perfect biscuit brown electrode dome

thanks guys, appreciate it

Just a guess kid but take the cover off the end of the power valve where the cables go on and make sure the PV isn't fouled up with oily crap or that the cables haven't seized . Always oil new cables . If the PV is seized , a strip and clean with new seals and cables will sort it ( I'm guessing that the PV is cable operated ) . If not , time to check the PV motor . Best of luck .

Sounds electrical to me. Power to the cdi would be my second check after making sure the battery was good. ie 12v.

Check the connections from the cdi to the mag as well.

Does the starter spin the engine or just spin.

Check to see if the pv blade isn't coked up too much carbon can be quite stubborn and make it stick ! Soak it in caustic soda you might aswell do the exhaust too while you at it, will make it sound a lot nicer failing that if the DT pv is run off a solenoid take the pv assembly off and do a test on a 12v battery to see if the magnet in the solenoid hasn't broken down. Hope this helps

thanks for all this guys

 

Ill have a look at the PV, does the PV cutting out have anything to do with why it wont want to start.

to test the battery im going to get a multimeter

I bought a whole new loom for it as it looks so terrible inside i was hoping after relooming that might be the solution 

 

 

Try another plug,    for a start,  then check for fuel ,[ flow out of tank, to carb]. 

Tried a new plug, good spark from old one too, checked the fuel line from tank to carb and it is freely flowing

No it isn't run from a solenoid, its run by the cdi direct. Yes that could be pricy but your not there yet. Don't automatically lube cables as some are designed with liners sensitive to hydrocarbon based lube which can swell. Use a silicone based lube if you must.

Unplugging the power valve should make no difference to the bike actually running, massive difference to power and rideability but it will happily start and run.

Are you getting a spark? Or have you tested it on something else?

I'm still thinking electrica not the cdi (yet) either. You have done things like checking the ignition switch is switching all its supposed to, wouldn't be the first time that's been at fault, or the kill switch, all go through the headlight the garage got wrong......

22 minutes ago, Cynic said:

No it isn't run from a solenoid, its run by the cdi direct. Yes that could be pricy but your not there yet. Don't automatically lube cables as some are designed with liners sensitive to hydrocarbon based lube which can swell. Use a silicone based lube if you must.

Unplugging the power valve should make no difference to the bike actually running, massive difference to power and rideability but it will happily start and run.

Are you getting a spark? Or have you tested it on something else?

I'm still thinking electrica not the cdi (yet) either. You have done things like checking the ignition switch is switching all its supposed to, wouldn't be the first time that's been at fault, or the kill switch, all go through the headlight the garage got wrong......

im sorry im really quite basic with mechanical know how, i just ordered a haynes manual to help me out.

do you mean check that its all wired correctly ?

could you elaborate a bit on this please

yes i am getting a good spark. plugged into the HT lead and then touch it with metal and it fires off a solid blue spark

thanks

Ah. The 'bright blue spark' was something you should have led with...

Ok tac change. Did the plug come out wet after your attempts to start it.

It would be worth looking up the exhaust port (after removing the pipe) as sometimes these engines clip the powervalve or the piston ring enters the exhaust port causing the same. 

That jams the valve and the piston damage loses all compression.

 

Ah ok thanks for that

 

ill take the whole exhaust off and have a look in

 

it sounds expensive if that is what happened

Not really. 100 quid therabouts.

30 for the rebore, 20 for a gen top end gasket kit and around 50 for the piston kit. Or therabouts with you doing the spanners.

Cost around 400 on my TDR. It may still be a bad connection but we need to check.

not a excellent day, got the carb off wanted to take it to bits to clean, and three underside screws were rusted and sheared off. i have a screw extractor to get them off.

can i take these sheared screws any B&Q type place and find replacements, or do they have to come from mikuni

Id be fine for doing a top end rebuild, slow methodically and reading a book about it though. yet to look in the exhaust port, as im preoccupied with the carb

Should find them no problem. 

The thread is known as metric fine. Pretty universal.

If you want to save massive future hassle get stainless allen screws instead.