100 miles in 4 hours...

To and from Chilton Didcot on the DT today. Must find a way
around Reading rush-hour the rest of the week. I might try hitting the
M4/A404(M) between Langley and Maidenhead to save some time too (shunned
the M'ways today because of the spray problem). Haven't hit reserve yet
after filling up last night[1]. Need oil soon -- the BP station at Knowl Hill
didn't have any in stock; at that point I seemed to have more than enough
to get home so I didn't try anywhere else.

Any suggestions as to why the engine hangs up at 3000 rpm for 30
seconds or more when I stop at lights, before dropping to a more
reasonable idle?

Bloody thing's a **** of a starter too (or I haven't learnt all its
idiosyncracies yet). I need boots with more shin padding...

[1] It took 3.4 l for the 40 miles since filling up after collecting it
from TOG. I make that around 53 mpg.

--
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...

Check the rubber inlet manifold for cracks and airtightness.

 

Thanks Loz, that was my first thought too but it's been a while
since I played with 2-smokes.

--
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".

 

.... and loose carb tops too.

--
Steve Parry
K100RS SE & F650
and a 520i SE Touring for comfort


(not forgetting the SK90PY)

http://www.gwynfryn.co.uk

 

Shitte in the fuel line. Clean float needle mechanism, tap, tank gauze,
fuel path generally, and if it works drop the needle jet a notch or
two.

 

Dr Ivan D. Reid says...

On a DT of that age I'd be looking for cracks in the rubber around the
part where it flattens out onto the flange mounting. You can check by
putting a solution of water/washing up liquid around the area and
seeing if it bubbles up when you wind the throttle on.

 

veal says...

Honestly Ivan, unless you've ported the barrel, don't piss about with
needle heights. Every single time I've been advised to do this it has
been at the expense of power or torque elsewhere in the rev range.
Leave the needle heights alone and sort the jetting if needed, which
I'd very much doubt on a standard bike.

The first thing I'd be doing on any reed valve stroker of that age is
junking the original steel reeds, as they crack and end up being eaten
by barrel and piston. Stick a set of fibreglass Boyesen reeds in.
Advantages are that if they do break then the engine spits the bits out
without any damage being caused, also they bring the power in lower
down the rev range and increase midrange torque.

 

Honestly Ivan, unless you've ported the barrel, don't piss about with

Fair point - my suggestion was based on the fact that the bike had
obviously been bought off some old bodger who may have compensated for
fuel supply problems by meddling with the carb. I was really suggesting
setting it all back to standard after a careful clean up.

I've never found the symptoms described due to leaks in the air intake,
but yo'ure bang on about the reed valves.

 

I checked the inlet this morning; the bolts holding the manifold
(unifold?) and reed block were a bit loose for my tastes, and so was the
carb clip. I thought I'd made an improvement but by about Maidenhead it
was hanging up at 3,000 again.

I'm not sure how much has been bodged (or were you talking about
TOG?). Given that it only had 2,000 miles on it, I'd hope he hadn't
screwed around too much. I'd be tempted to drop the main-jet a tad if I
were sure it wasn't going to see motorway duty. It splutters a bit at
6-7,000 rpm and doesn't rev cleanly to redline; the plug is sooty around
town but that's probably to be expected. I think the needle's close to
the money as the mid-range is as clean as you could expect, but perhaps
needs richening on the idle screw.

Well, Boyesen reeds (and playing with the needles...) won me an
F2 race in Canada, so they can't be all bad.

But anyway, today was another story. I found my way to Sonning as
planned, but the wheels fell off when I tried to get to Goring. Ended up
on a green-lane in some place called Harpsden Bottom -- well it was
actually single-track bitumen, but with so little use that it was covered
in moss... Finally saw a sign for Cane End and that straightened me out.
47.5 miles in 1h30" (Oh, I'd filled up with 6.3 l for yesterday's 100
miles and topped the oil tank right up with about 800 ml of 2T.).

So, coming home I was pretty sure what to do; Goring, Sonning
Common, Sonning, Maidenhead, home. Nope, missed a crucial side turning
'cos I was looking for a T junction next; ended up in a dead-end called
Mapledurham through more single-track roads. Turned out I wasn't too far
out but the signs at intersections only gave very local pointers.
Backtracked to Goring Heath, and back on the right road -- but no signs
for Sonning at Sonning Common... Ended up in Reading outskirts and could
only find signs for Henley, not Maidenhead. Following on these I came on
a roundabout that was identical to the one I'd turned off the A4 to
Sonning at this morning; puzzled, I backtracked when I should have kept
going and so came to Henley. And very slow crosstown traffic. But then
the road from there to Maidenhead led onto the A404 -- Aha! I was going
to try the motorway between there and Langley, let's do it in reverse.

So, I'm belting along the M4 at 7,000 rpm and the speedo showing
about 50 mph (which it does in top for any revs above ~6,000) when this
semi pulled out to overtake. The bike slowed. "Hmm, strong bow-wave
effect! Nope, I'm out of petrol, at 97.5 miles since filling up this
morning." As I groped for the petrol tap and the bike slowed dramatically,
White Van Man behind kept blissfully towards me at 80 mph until it was
*very* close to too late.

A mile or two later came Exit 5, so I pulled off and into Langley.
Spotted the turn to Iver -- and the bike died as I pulled up at the
lights. No starty. Bugger. Into a "safe" island between the
straight-ahead and turning lanes. Spark? A bit. The plug was a
reasonable colour for having just done 10 or 12 miles close to redline --
a touch grey perhaps -- and bone dry. It gave one whoof when I tried agin
but then nothing. Bugger. A nice young lass on a 600F or so stopped to
ask if I needed help, I said "not yet, and I'm not that far from home" so
on she went.

I pushed the bike across the ped crossing and down the Iver road
to a little car park. Filter bowl off -- fuel runs. Carb drain plug/main
jet cover off -- carb drains onto cooling engine. Some trouble getting
plug back in, and it nips up tighter than it came off. About to try
something else when I spot the O-ring in the puddle of fuel on the ground.
Oops. Look at spark again. Still not impressive. Thumb over plug hole.
Is *that* all the compression there is? Biro down plug hole at TDC can't
feel any piston holes. Close plug gap down a bit and try again. Still no
joy. Last resort, the car-park has a slight downward slope. Snick into
second, run halfway across, dump clutch -- it spins! And lights up. But
dies when I let it back to idle. Starts on the kick, so I try to keep it
alight while I re-dress. It dies and won't kick again, so fully-clother
in helmet and 2-piece leathers I try running it again...~

Successs, and to cut a long story short, I got it the few miles
from Langley to home by making sure revs never got below 4,000 rpm all
the way. Of course, I hit every damned red pedestrian light in Langley
first.

So now, I don't trust it until I get a new plug and clean the
carb -- I suspect some crud slipped through the filter when I turned
to reserve and blocked an idle passage or maybe something cracked in the plug
when it cooled after the motorway stint. So it'll be up at 6 am still the
next two days to catch a train out to Didcot rather than trying to get that
elusive perfect run where I don't add bars to my SKOGA.

Lozz, is there anywhere that'll do a mail-order on the Boyesen reeds?

--
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...

Try M+P

http://www.mandp.co.uk/list.aspx?tier1=Tuning&tier2=Reeds&tier3=Hy-Tech