400-4 bogosity.

Took the beastie out for a pre-MOT test ride.
Something is definitely not right, it has the flatspot from hell at
around 2/3 throttle and after about 3 miles it could not even hold
4th gear on the level without slowing. Seemed to be running hotter
than expected, so I suspect that it was starting to nip up.

Sounds like a carb/fuel issue to me, I'll take them off (AGAIN) and
check that the main jet size agrees with the BOL and that no more
crap has appeared in the float bowls.

Grrrrr.

Any other inspirations ?.
Also the front brake seems a tad useless to me, less stopping power
than the drum rear, I would have thought it should do better than that.

 

Now that's not good.

Fitted inline filters yet?

Ultrasound cleaning of the carbs might be very helpful.

Very carefully disassemble the whole mechanism including the swinging
arm, regrease with the appropriate greases and once you made sure that
everything is working as Sochiro intended, put back together.

They should only be lethal in the wet.

 

Wasn't raining was it?

 

See if running with the fuel cap open makes any difference. A
blocked air breather can cause similar time-dependent problems and IIRC
they were mostly through the cap and easily blocked in that era.

Upgrade to GS550B brakes. <g,d&r>


--
Ivan Reid, School of Engineering & Design, _____________ CMS Collaboration,
Brunel University. Ivan.Reid@[brunel.ac.uk|cern.ch] Room 40-1-B12, CERN
GSX600F, RG250WD "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".

 

Sounds like it could be a timing issue to me, so try the ATU. They can
catch and stick sometimes, with odd effects. Also check that the
points are a) the correct ones (mine weren't) and b) solidly mounted.

They all do that sir. TOG always points at a seized mounting arm,
which is supposed to swing freely. The one I had was fine in that
respect, but still completely useless. A partial strip of the calipers
revealed pads which looked like they'd fossilised a decade beforehand,
plus mucho shit around the moving bits.

Easily resolved, and with the addition of braided hoses to replace the
near-perished originals, they were good enough to lock the front,
although as the 10+yo tyre was about as grippy as a fried egg on a
teflon pan that didn't take much. But it brought the braking ability
up into the 20th century, at least, and made the front better than the
rear.

 

If it's been off the road for a while it'll be bunged carbs, for sure.
Poper ultrasound cleaning, new O-rings where appropriate, new needles
and jets, the works. Budget a couple of hundred.

The front brake can be made to work OK. The swinging arm pivot should be
free, of course. The piston shouldn't be seized. Then it's a matter of
steel hoses throughout.

I've got a dogleg lever fitted to mine. Makes a difference too.

At this point, if I were in your shoes, I'd recognise it's a money pit
and break it for spares.

 

I'd say you would have started breaking it a *lot* earlier.

 

Heh. Well, I had enough sense not to buy the thing in the first place.

 

Indeed, but our objectives are maybe different.

To me the fettling is the hobby and the challenge. As a pensioner I can
spend endless hours tinkering to keep me busy instead of sitting in
front of the idiot's lantern.

I may have bitten off a little more than I can sensibly chew with this
one but time is on my side. Eventually all of the impossible bits will
show up for peanuts on fleabay and be replaced. I may lose a little
money but the journey and experience will probably be worth it.

The carbs will be stripped again and very carefully cleaned. I must
have missed something last time. I suspect that an inline filter is
required to stop shite getting through from the tank.
First, however, I plan to try draining the tank via the tap to check
that the flow does not slow due to a blocked breather. It could be
that simple.

 

Fair enough. But I can smell 'money pit' already.

Um, now, they won't. Not for peanuts, anyway. I've noticed and remarked
that good SOB spares are getting pricer by the year.

Best thing to do is buy a donor bike, take what you want, and flog the
rest. Seriously.

That's a good idea.

I doubt it. I really, really doubt it. So many people parrot "blocked
breather stopping fuel flow" because they've heard it many times
themselves.

In well over 30 years of messing around with bikes, hundreds of 'em, I
have never, ever had it happen. Nor has anyone I know.

 

<waves>

I've had it on the T4 Tiger, as have others. Never on any other bikes
though.

 

You're not alone in this.

Especially for popular bikes like 400 Fours.

Trouble is that the parts that are likely to be duff will drive up the
price of the donor bike, too. I wouldn't be surprised if the donor bike
ended up costing the same or more and then turn out to be the better
bike.

 

<Life of Brian mode>

There's always one, isn't there?

 

You dont have a tank bag then .......

 

Life would be boring if there wasn't. Tbf though the whole tank on T4
Tigers is a disaster area. I think Triumph decided to stick all the
bike's design faults in one area (with the exception of the early
sprags).

The cap has a stupid rubber one-way flap thing over the breather hole,
which tends to **** up. The captive nuts around the bottom edge for the
fairing bolts can start to spin in their housings if you let a dealer
anywhere near it, which means drilling into the tank to fix them (&
hoping you don't drill too far), & if you leave the tank off the bike
for any length of time, it changes shape & won't fit back on again.

They carried this crap design trait on with the T7 Tigers too - fuel
guages that fail regularly & pick a level out of the ether when they
are working, & fuel pipe connectors that break, spraying petrol all
over the engine.

 

Happened on Ginge's ZXR12 on a 2005 French trip. Would start OK, run
fine for a bit, then splutter and stop, refusing to start unless left
for five minutes. The breather tube wasn't blocked, but kinked, from
something he'd done around the battery area a week or so earlier.

The oddest thing was that he'd ridden all the way from the UK to
Bergerac with (IIRC) no problems at all. Still, once found, the fix
took all of 30 seconds and the problem never recurred.

 

Or ZRX, or whatever. The Eddy Lawson replica replica thingy.

 

Heh. Good point. Yes, I do, but it's never blocked the breather.

I've had a tank bag strap block the airbox inlet before, though. That
caused some head-scratching.

 

Hi there,
When your engine was running a bit sick, did your check the exhaust
pipes to see if all cylinders were running. If 1&2 were hot and 2&3
were cold or vice versa, check coil/points.
T.W.

 

It has happened to me.

Back in 1977 I spent a very pissed off night pushing an ST70 from
Kilburn to Harrow only to to find in the morning that the petrol tank
cap breather was blocked. Yes, blocked, not turned to the closed
position.