DT175MX technical data

Does anyone have a DT175MX service manual[1] or know these data
off the top of their head (roughly in order required)? I've yet to find
any data on-line.

o Standard spark plug and spark-plug gap.
o Standard idle-screw setting.
o How to synchronise the oil pump with the carburettor.
o Standard main-jet size.

[1] It seems there's a Clymer manual; it goes for $20-25 in the US, or
£20-25 in the UK (see e-bay).

--
Ivan Reid, Electronic & Computer Engineering, ___ CMS Collaboration,
Brunel University. Ivan.Reid@[brunel.ac.uk|cern.ch] Room 40-1-B12, CERN
GSX600F, RG250WD, DT175MX "You Porsche. Me pass!" DoD #484 JKLO# 003, 005
WP7# 3000 LC Unit #2368 (tinlc) UKMC#00009 BOTAFOT#16 UKRMMA#7 (Hon)
KotPT -- "for stupidity above and beyond the call of duty".

 

Dr Ivan D. Reid says...

Somewhere in amongst all my shite I have a genuine Yamaha set up data
book from that era, but as we've just moved house I'm buggered if I can
lay my hands on it. I'll try and search it out later today.

 

Thanks. I found an NGK site which specifies a B9ES plug at .032"
.... it currently has a B8ES at something less than 32 thou.

--
Ivan Reid, Electronic & Computer Engineering, ___ CMS Collaboration,
Brunel University. Ivan.Reid@[brunel.ac.uk|cern.ch] Room 40-1-B12, CERN
GSX600F, RG250WD, DT175MX "You Porsche. Me pass!" DoD #484 JKLO# 003, 005
WP7# 3000 LC Unit #2368 (tinlc) UKMC#00009 BOTAFOT#16 UKRMMA#7 (Hon)
KotPT -- "for stupidity above and beyond the call of duty".

 

Dr Ivan D. Reid says...

Synching the oil pump is easy, if it is like any other 2-stroke Yamaha.
First, adjust the throttle cable to give about 0.5 to 1mm play at the
twistgrip. Then wind the plastic pinion (used for bleeding the pump) at
the back of the oil pump so that there is maximum clearance between the
pulley and the pump body. Set the plunger so that there is 0.20 to 0.25
mm clearance between the pulley and the pump body. To adjust the
clearance you remove the locknut and shim it out to suit. If the
adjustment is correct, on a closed throttle the pin on the pulley
should line up with a mark on the oil pump itself.

As yours has so few miles on it, I'd very much doubt it will need
shimming to suit. I've only had to do this a couple of times and that
was because some numpty owned it before me.

On second thoughts, if I were you I'd check it really carefully

 

I'm not saying that's wrong, but it does seem a bit on the large side.
I'd get confirmation from elsewhere otherwise it could be rather
retarded...


Regards,

Simonm.

 

I think that you're thinking points gap, not plug gap here.

 

I have a HBoL for '71-'85 bikes that mentions the MX in a later
chapter. Unfortunately it doesn't explicitly list the MX in the
specifications.

I saw references to DT175 A, B, C, E, F, G & H and the frame prefixes
1G1, 2K4, 2X2, 4J4. Otherwise it just says "all other models".

What year is yours? If it falls within this manual's range then you're
welcome to it.

 

It's an '81. I'll try to demung[1] your address, thanks.

[1] The canonical definition of "mung" is recursive: "mung until no good".

--
Ivan Reid, Electronic & Computer Engineering, ___ CMS Collaboration,
Brunel University. Ivan.Reid@[brunel.ac.uk|cern.ch] Room 40-1-B12, CERN
GSX600F, RG250WD, DT175MX "You Porsche. Me pass!" DoD #484 JKLO# 003, 005
WP7# 3000 LC Unit #2368 (tinlc) UKMC#00009 BOTAFOT#16 UKRMMA#7 (Hon)
KotPT -- "for stupidity above and beyond the call of duty".

 

Nope. If you increase the _plug_ gap, I think it also retards the spark
(obviously the points gap does this far more, but for entirely different
reasons).


Regards,

Simonm.

 

You're a GNU fiend, aren't you?

 

You're a GNU fiend, aren't you?

 

Not really, but I think I corresponded with Eric Raymond once --
about something other than the Dictionary.

Dennis Ritchie once said something complimentary about me...

Did I say that the OO course I was on last week was given by
John Deacon? Not the drummer. Not the PD racer. Just a BMW-riding
software expert.

Here endeth the name-dropping.

--
Ivan Reid, Electronic & Computer Engineering, ___ CMS Collaboration,
Brunel University. Ivan.Reid@[brunel.ac.uk|cern.ch] Room 40-1-B12, CERN
GSX600F, RG250WD, DT175MX "You Porsche. Me pass!" DoD #484 JKLO# 003, 005
WP7# 3000 LC Unit #2368 (tinlc) UKMC#00009 BOTAFOT#16 UKRMMA#7 (Hon)
KotPT -- "for stupidity above and beyond the call of duty".

 

I guess I have to step up to the plate again, as this is the field
that I got my PhD in...

Yes, I couldn't argue with that at all. Higher gap -> higher
break-down voltage.

Well, I was hoping to avoid that. I suppose I could google for
typical spark-voltage rise-times, etc, but my overall impression is
that it's "bloody fast", especially after CDI-type ignitions replaced
magneto-and-points spark generators. (I'm hoping the DT has pointsless
ignition... Certainly the spark was blue enough with the new plug that
I thought, "That doesn't look like a Kettering system!") The time to reach,
say, 30 kV is probably not much more than that to get to 25 kV. Ah,
the first URL that came up on google:
http://www.jetav8r.com/Vision/Ignition/CDI.html -- contains more than you
ever need to know about ignition and gives spark-voltage rise-times as
"typically 80-120 microseconds for induction systems and 6 microsecond for
CDI." So your original point may have had some validity for older points
systems.

As an aside, the one thing that I noticed myself having an effect
on my first bike -- a Suzuki 100 -- was the spark-plug heat range. A
colder plug definitely changed the power-band to sharper and stronger;
I've always acribed that to the marginally higher compression ratio
because the plug volume was smaller than the warmer plug (due to the
extra insulator).

That's right, as soon as one gap sparks, the potential actually
drops (due, inter alia, to the voltage drop across component resistances
once current actually starts flowing) so if you haven't reached break-down
voltage on the other gaps, it ain't going to happen. It'd be quite a
coincidence to get sparks on more than obe gap simultaneously, methinks.
A hot-spot is probably not a good idea; it could promote dieseling/pre-
ignition, which you don't want, and even if it made the spark "easier"
this would mean a spark at a lower voltage and less energy, which you
probably don't want either.

I could vaguely think of a situation where you might if you had
one of those multiple-spark igniters (I think they were a brief fad) where
the first gap to fire won't sustain a spark on the second spike so another
gap would fire, but it might not stand up to rigorous scrutiny.

--
Ivan Reid, Electronic & Computer Engineering, ___ CMS Collaboration,
Brunel University. Ivan.Reid@[brunel.ac.uk|cern.ch] Room 40-1-B12, CERN
GSX600F, RG250WD, DT175MX "You Porsche. Me pass!" DoD #484 JKLO# 003, 005
WP7# 3000 LC Unit #2368 (tinlc) UKMC#00009 BOTAFOT#16 UKRMMA#7 (Hon)
KotPT -- "for stupidity above and beyond the call of duty".

 

Right. As you're now The Sparks Expert (though possibly not the
combustion expert), does a weak spark cause poor efficiency etc simply
due to misfires or due to the combustion "not getting off to a good
start" as it were? I've always assumed the former.

 

'Twas only those I was thinking of. The sharper the leading edge of the
LT switch off, the greater the back EMF risetime on the HT side of the
coil .: the less the points gap will have an effect on timing.

I find small 2-stroke tuning fascinating - just the right amount of
controllable and uncontrolled variables for endless fun

Indeed. I think they were just another snake-oil thing really, the
hot-spot comment was simply because I can't think of another reason why
they might improve performance. But then I couldn't get them to work any
better either, never mind actual gap setting, which was a right pain.

Incidentally, I *can* see an argument for larger gaps on electronic
systems: the greater length of the spark ought to make ignition
smoother, but it presumably needs more robust electrodes.


Regards,

Simonm.

 

Yes, it was the "gaseous electronics" part rather than any
combustion technology. A bit of both, I'd have thought. If you are getting
the ocasional misfire but have enough engine speed/flywheel momentum not
to notice then your efficiency would decrease. However, if the spark's
weak enough that you have to reduce the gap, etc, or you're not getting
a very "fat" discharge, then you're not putting as much energy into
the initiation as you might and the initial stages of combustion will be
slower (effectively retarding timing again, I guess).

It's all a bit of a black art. It's only been in the last several
years that it's been realised that metastable species (i.e. radicals)
from incomplete combustion (to simplify...) remaining in the incompletely
scavenged cylinder will affect the efficiency of combustion on the next
power cycle. Under the right conditions you can make an engine where
you don't even need the plug once you're under way[1]. I think it was
Honda who won a Paris-Dakar or two with such an engine.

[1] But not a diesel -- without high compression ratios and injection-
initiated combustion.

--
Ivan Reid, Electronic & Computer Engineering, ___ CMS Collaboration,
Brunel University. Ivan.Reid@[brunel.ac.uk|cern.ch] Room 40-1-B12, CERN
GSX600F, RG250WD, DT175MX "You Porsche. Me pass!" DoD #484 JKLO# 003, 005
WP7# 3000 LC Unit #2368 (tinlc) UKMC#00009 BOTAFOT#16 UKRMMA#7 (Hon)
KotPT -- "for stupidity above and beyond the call of duty".

 

I've used GNU stuff but had to google for Raymond. I'm happy to say I
knew of Ritchie and the other two Deacons.