Author Topic: DT1 250 w/ PVL  (Read 2879 times)

0 Members and 1 Guest are viewing this topic.

Offline DCPlasticsguy

  • C-Grade
  • **
  • Posts: 61
    • View Profile
DT1 250 w/ PVL
« on: September 20, 2013, 12:23:04 pm »
I'm having one heck of a time getting this thing to run correctly with a new PVL ignition. It seems as though I have tried every timing position available. I started at 2mm BTDC, went to .5 and then out to 4 with increments in between as well. I'm using the timing mark next to the arrow that is pointing counter clockwise. The bike will start, but it backfires/pops and has squeal to it. The engine has new main bearings, crank, top end, seals, etc. I don't see any leaks. The spark is nice and blue when I take the plug out and check it. Any advice guys?

Offline Freakshow

  • Superstar
  • ******
  • Posts: 7277
  • Adelaide, SA - looking for a "YZA" tank
    • View Profile
Re: DT1 250 w/ PVL
« Reply #1 on: September 20, 2013, 01:04:24 pm »
OK when you set them up did you put the right air gap in there ?  you need to fit the rotor properly, then there should have been tape on it that when you put the stator on you adjust the blades in so they just touch it, you need to have the same air gap all the way around.  If you lost it just put a piece of masking tape on it but dont overlapp.

When you put your hand on the kick starter and press down is th erotor going the direction you think it is ?  then ther eis an arro on the stator that point in the same direction that make on that one is the timing slot you use.  set it at under 2mm btdc with a Guage in the spark hole.

these things are idiot proof, your doing something simple not right.  best you back track.  also make sure you are NOT using a resistor plug ( if there is an R in the code remove it and fit a 8EG or 8EGV)

Was the bike running before you changed the ign ? you dont have part of a rag in the inlet or outlet still do you ?
74 Yamaha YZ's - 75 Yamaha YZ's
74 Yamaha  flattracker's
70  Jawa 2 valve speedway's

For sale -  PRE 75 Yamaha MX stuff, frame, motors and parts also some YAM DT1,2,A and Suzi TS bikes and stuff

Offline BETRIC

  • A-Grade
  • ****
  • Posts: 312
    • View Profile
Re: DT1 250 w/ PVL
« Reply #2 on: September 20, 2013, 03:11:34 pm »
Have you identified the correct timing marks on the stator plate as I know that the instructions have been a bit fague in the past, later issue instructions now state the following ( PVL stators have a 3/16" straight line timing mark stamped onto each leg of the stator frame, use the timing mark that is closes to the arrow on the stator indicating the direction of rotation of engine.) have close look at the stator, you will see the the 3/16" timing mark is there, it does not stand out well on the stator.
DELTEK, 72 MINI TRAIL, 73/4 XR75, 77/78 XR75, DG MONOSHOCK FRAME XR75, REDLINE FRAME XR75, PK RACING MONOSHOCK FRAME XR75, JWRP XR FRAME, SL70K1, 81 CR80RB, TY80A/B, YZ80A/B/D, GT50/80A, GTMX80A, 73 GTMX, GT1, COOPER MX, COOPER ENDURO,MX360A,MX250B,YZ125X MX100, 72 XL250, TC100,TL125, TY250C,IT250J

Offline Purple Dave

  • A-Grade
  • ****
  • Posts: 473
  • Just call me...ALVIN !!....courtesy of Slides 29 !
    • View Profile
Re: DT1 250 w/ PVL
« Reply #3 on: September 20, 2013, 05:21:35 pm »
Have you identified the correct timing marks on the stator plate as I know that the instructions have been a bit fague in the past, later issue instructions now state the following ( PVL stators have a 3/16" straight line timing mark stamped onto each leg of the stator frame, use the timing mark that is closes to the arrow on the stator indicating the direction of rotation of engine.) have close look at the stator, you will see the the 3/16" timing mark is there, it does not stand out well on the stator.

Very good advice Betric........I was using the wrong timing mark to start with and my SC 500 was popping and spluttering also....
does your forum name relate to Betric Private Hospital ? ???
Dirt Track Racer late 60's/throughout 70's

Offline BETRIC

  • A-Grade
  • ****
  • Posts: 312
    • View Profile
Re: DT1 250 w/ PVL
« Reply #4 on: September 20, 2013, 06:44:23 pm »
Dave I use to ride for Betric racing in the early 80's, the owner of the team owned the hospital.
« Last Edit: September 20, 2013, 06:47:20 pm by BETRIC »
DELTEK, 72 MINI TRAIL, 73/4 XR75, 77/78 XR75, DG MONOSHOCK FRAME XR75, REDLINE FRAME XR75, PK RACING MONOSHOCK FRAME XR75, JWRP XR FRAME, SL70K1, 81 CR80RB, TY80A/B, YZ80A/B/D, GT50/80A, GTMX80A, 73 GTMX, GT1, COOPER MX, COOPER ENDURO,MX360A,MX250B,YZ125X MX100, 72 XL250, TC100,TL125, TY250C,IT250J

Offline OverTheHill

  • Legend
  • *****
  • Posts: 801
    • View Profile
Re: DT1 250 w/ PVL
« Reply #5 on: September 20, 2013, 10:35:23 pm »
 Considering it runs i think i'd strobe it to find the firing point of the stator in relation to the rotor in-case it's not firing when you think it is [say at 2.5mm ball park] then mark that point with something [white twink correction fluid's good]. Now you know for sure when the stators firing. Check that against piston position btdc,  if wrong then move the stator around to get the desired advance. Not up with the PVL system but if stator can't be moved & rotor's not keyed then [now knowing the firing point] just move the crank to 2.5 btdc & reset the rotor to your 'white twink' marks.
In saying that--if all else fails then bolt on an original flywheel mag purely to make sure something else unusual isn't wrong with the motor like [i dunno] RH crank seal popped out but she'd be smoking heaps if it ran at all. Seen some odd ones over the years with reed valve pistons [DT2 type] in back to front & home made base gaskets with transfers 'not' cut out etc. Anyway, hope you get it sorted. Cheers. ps, forgot to factor in advance/retard characteristics if the PVL has that but anyway--starting point for diagnosing!!

Offline BETRIC

  • A-Grade
  • ****
  • Posts: 312
    • View Profile
Re: DT1 250 w/ PVL
« Reply #6 on: September 21, 2013, 03:41:00 pm »
The PVL's are easy to time once you identify the correct timing mark on the stator, I run them on my MX 360/250 YAMAHA's, and a few of my XR75's
DELTEK, 72 MINI TRAIL, 73/4 XR75, 77/78 XR75, DG MONOSHOCK FRAME XR75, REDLINE FRAME XR75, PK RACING MONOSHOCK FRAME XR75, JWRP XR FRAME, SL70K1, 81 CR80RB, TY80A/B, YZ80A/B/D, GT50/80A, GTMX80A, 73 GTMX, GT1, COOPER MX, COOPER ENDURO,MX360A,MX250B,YZ125X MX100, 72 XL250, TC100,TL125, TY250C,IT250J