[DT 175 mysteries]

Hi forum 

I did try to get to the bottom of an issue I had a while back but never really got there so hoping this time I can get to the bottom of it 

76 DT175

Bike runs ok (although air screw pretty much full in),  can start easily with No choke, pulls well..for a while 

After 10 15 mins it  suddenly loses power and lots of blue smoke seems to be worse if forced to idle, say in traffic 

Put a new carb on it 

Burnt out exhaust with heat gun

Running with  air filter 

Running on oil pump

Would crank seals cause this?

Weak spark from primary coil breaking up when hot?

Any suggestions or knowledge most welcome before I just start throwing parts at it

Thanks in adv

D

 

 

 

 

[DT175 air leak?]

1 hour ago, blackhat250 said:

Ok , is it good for compression when cold, .does it feel tight to kick -over, ? 

 

feels about right i guess, again not too much to compare it to really as this bike has always had this issue in one form or another since picking it up end of last year.. thought it was rust in tank, then carb, blockage in exhaust, all of the work done (new carb, decoked exhaust, tank lined) improved the issue and overall performance but it is still present, will look at getting compression tested and check seals, anyway to do this without cracking the cases? perhaps wd40 around the seal while running?

thanks again

[DT175 air leak?]

7 minutes ago, blackhat250 said:

You know digger,", my dt 175  sounded a lot better, esp at tickover,   yours sounds limp,   am saying its rebuild time, maybe am wrong,, 

haven't got much to compare it to really to be able to decide if this is correct diagnosis but i will say off the bat from cold it goes like stink and doesn't miss a beat, only after the 10 minute period does it start to act up

1 minute ago, Cynic said:

With how slow the revs drop and how wimpy and flat the engine sounds the seals have to be high on the list.

How does it start in poor power mode.

hard to start tbh without presuming to know too much i would have thought seals would be a more gradual decline in power with perhaps the idle not returning to base quite so quickly but its probably my next port of call

[DT175 air leak?]

On 3/20/2018 at 8:08 PM, blackhat250 said:

So more air is curing the problem ?,  does this carb have an  0  ring on the emulsion tube ,?

unsure as haven't had it apart yet as its new, decided to change the old one out as i was convinced it was carb issue

here is a vid of it doing its power drop thing, as you can see it drops on idle quite suddenly after 10 or so minutes of riding and is accompanied by subsequent drop in power

this is recorded after 10 minutes of riding, idle set to 2k from cold, then aftrer 10 minutes and presumably when hot loss of power and idle down, you can see this clearly at 24 seconds or so in

 

[DT175 air leak?]

weird thing come to think of it was briefly disconnecting the oil feed to carb seemed to bring it all back to life?

haven't tried this with new carb so it may have been just a coincidence

will de-coke and update and if it persists try removing oil feed again to see if it makes a diff

D

[DT175 air leak?]

yeah i think so too, thanks

looks like torch to get it hot the heat gun?

this looks probably a little quicker?

 

[DT175 air leak?]

Hi forum

Just wanted to update this thread. Well not really an update as I still haven't got to the bottom of this issue..

Basically runs great for 15 to 20 minutes then runs like crap, will rev but no power and idle goes down to where it won't idle without some revs

time factor always seems fairly consistent, so perhaps a heat issue of sorts?

plug dry-carbon fouled

about to de-coke the exhaust next..perhaps its getting gunked up and the heat is making it gasp for air?

then piston rings..

then perhaps crank seals?

have just replaced carb with a new one as it was leaking from float bowl

would greatly appreciate any thoughts on this

D

 

 

 

[DT175 air leak?]

Yes thats the kiddie

Mine may have a little more "patina" I guess..

Good call about jet will grab a few sizes and try them out, also check for water in carb, tried again today and screwing air screw in did actually stall the bike without air filter, seems ro want to run better with screw out 3.5 turns so it seems to wanting more air, or getting too much fuel, pulling out choke stalls it instantly in any condition, will start without choke easily...once.it stalled.on air screw was hard to start and idle was down.for a while if that helps shed any light on it

Thanks

D

[DT175 air leak?]

Hi forum

DT175 76 twinshock

been having some troublesome issues with my DT of late, any advice would be greatly appreciated?

had the bike suddenly lose power on me and limped home a few months back

since then have:

..rebuilt carb

lined tank, some rust issues

new fuel filter

set points

new air filter - came without one but still doesn't have air filter cage

primed oil pump

checked piston and barrel-all good

got back to running well, loads pull idles well

ran well for a couple of days until today when it started losing power on run to work, smoking (not Blue) also from air box

took it to mean air filter was fouled again so removed it and was running better but lacked pull on run home

since then have checked air screw on carb and can screw it all of way in and it has very little effect

so am thinking air leak and running lean?

crank seals next on the list then..

any other advice inbetween would be bloody marv

thanks

D

 

 

 

[80 xt250 stator issues]

attack of the zombie thread...!!

have replaced the source coil with a brand new old stock unit, the ignition coil replaced,new cdi, have just had the bike completely rewired back to standard and now cutting out after 10-20 mins, pops backfires and quits, then starts fine once cooled...

i will try another cap, plug and ht lead tomorrow

but if anyone has any pointers related to this behavior?

am getting tired of pushing it home...and spending money

JJ

[80 xt250 stator issues]

Thats a very simple generator and it will be very easy to sort out.

If you plug the lighting coil into the CDi it will blow it. It may actually work but this coil is capable of producing a lot of current which will burn out the SCR in the CDi box.

I've not tried the other unit. What I will say is the reason we started making CDi units for the SR500 was their one for this bike was shockingly bad. What they call a 'performance timing curve' is a joke as they keep the ignition fully retarded until 5,000 RPM when it swings full advanced

We've a nice little 12 volt conversion for the XT250 ;-)

This is the go I think, Thankyoui

May I just confirm this would replace my blown CDI?

So I wouldn't need to purchase a new/sh CDI in addition?

Bearing in mind the wiring on my bike isn't standard

Would ther be any way of you supplying me with the original colour coding for the stator assy so I have a basis to go on?

I can then bell it out and the only think I could get wrong would be polarity which is easily sorted?

I will probs sling an email via your site also

Ta

J£

http://www.rexs-speedshop.com/epages/es143131.sf/en_GB/?ObjectPath=/Shops/es143131/Categories/Products/12_Volt_Conversions

[80 xt250 stator issues]

Hi thanks

Yes certainly something is wrong somwhere in the way its currently - no pun intended -plugged up

Have got the stator apart again so I can trace cables back

Essentially I have 6 wires

2 from pick up coil

2 from lighting and 2 from source coil..

When you say high and low speed which coils are you referring to ?

Below is the diagram of my assy

There is a lighting, pick up and source coil marked on it

http://www.cmsnl.com/yamaha-xt250g-dual-purpose-1980_model8766/partslist/B-08.html#results

Sorry to be such a novice btw and any advice is greatly appreciated

Also if I accidently plug the lighting coil to the cdi could I fry either a coil or CDI?

Also anyone have any experience with a hyperpack cdi on a 6v xt250?

Thanks again

JJ

[80 xt250 stator issues]

Hope you won't mind me making my intro via a fiendishly complex problem

Recently had some issues with the bike(1980 xt250) intermittently cutting out

Traced to a snagged wire or two in the stator

Now I have rewired but the prev owner wired the bike in green throughout making plugging the stator back up quite a challenge

Six cables out of the stator

My method thus far is to plug 1 to 1 (1through6)

Then 1-2 (1through6)

I Pull the plug and check for spark when I get one I sling in the plug and tentatively give it a kick

I have found a few configs so far that seem to work ok, one which gives me spark

One which starts easy but runs a bit flat

Another that gives me good pull that puts a smile on my face but won't start cold (starts fine warm)

I wondr if anyone has a solution for this puzzle or could at least pm me with a wiring diagram?

Thanks in adv

JJ