Flummoxed by Suzuki GN250

Every now and again you come up against an odd one. A *really* odd one.

After I'd bought the GN250, I gave it a full service which included
setting the tappets, naturally, and I was getting a slight tick from the
top end.

It sounded exactly like a tappet that was fractionally too wide, though
oddly the noise didn't persist when you revved it hard, but I shrugged
and decided I'd look at it again when I got back from South America.

So this afternoon, I checked the tappets again to see if I'd got one
slightly out, but they all seemed OK. I reset them anyway, towards the
tighter end of the recommended clearance scale.

And damn me, the ticking seemed louder when I restarted it. Much
head-scratching and the odd swear-word.

It's sorted now: source of the noise traced. A virtual pint to anyone
who can guess what it was. A new one on me, certainly.

 

Crocodile?

 

In communiqué <1jcs7q7.rbo7w9m78zeiN%>,

You've got a screw loose.

--
+-------------------------------------------------------------------+
| Pete Fisher at Home: |
| Voxan Roadster Yamaha WR250Z/Supermoto "Old Gimmer's Hillclimber" |
| Gilera GFR * 2 Moto Morini 2C/375 Morini 350 "Forgotten Error" |
+-------------------------------------------------------------------+

 

He's behind you!

 

I know I have, but what about the bike?

 

In communiqué <1jcs8wr.1kagdtigaaeeuN%>,

OK , a long shot based on experience with a SO Talbot van engine.
Exhaust joint gasket (if there is one). On the Talbot it was a tiny blow
in the manifold gasket. Sounded just like a tappet at idle but drowned
by other noise at higher engine speeds.


--
+-------------------------------------------------------------------+
| Pete Fisher at Home: |
| Voxan Roadster Yamaha WR250Z/Supermoto "Old Gimmer's Hillclimber" |
| Gilera GFR * 2 Moto Morini 2C/375 Morini 350 "Forgotten Error" |
+-------------------------------------------------------------------+

 

Tappet too tight, piston hitting valve.

 

Good call, and I checked that myself, but no.

 

<offended>

I'm not *that* much of a bodger.

 

Like Mark Olson, a bloody good call, and I know what you mean, but no,
it wasn't this. It was one of other things I checked, though.

 

Err, decompressor not fully disengaging?

I've also had ticking from a valve not closing properly - the tick
actualy came from the exhaust. But that was a misplaced shim and I
guess the GN is screw 'n' locknut, so can't be that.

 

No-eyed deer. Four strokes are a mystery to me. I used to change
the shims on the GS550B, and tweak the cam-chain tensioner, but that's
about the limit of my technical experience.

--
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".

 

Don't think it has one, actually.

Screw & locknut it is. The clue was in the word 'tappets'.

 

Locknut had vibrated itself off the screw.

<Looks at GSX behemoth>

DAMHIK, IJD OK.

 

hmmm.

You've fixed it quite quickly so I guess nothing drastic. I was thinking
exhaust, head gasket or rattling carb slide.

Summat loose.

Give up.

 

Someone had fixed a playing card to the camchain with a clothes peg?

 

Nope. That in itself doesn't make the noise (er, unles it falls into
something crucial), but the opening out tappet certainly does. Had it
happen to me, too, once.

 

Tacho cable/drive.

I noticed that the shrink-wrapping, round the end of the tacho cable at
the cylinder head, had ridden up slightly, and so decided to push it
down to prevent any ingress of dirt and crap, and as I touched the cable
the noise stopped.

Huh? HUH???

I waggled the cable this way and that slightly and the ticking started
or stopped according to where the cable was sitting.

So I guess there's a fraction of play in the worm drive to the cable.
Anyway, that's it.

Like I said, a completely new one on me. I was certain it was a loose
tappet. It sounded identical.

Even after nearly 35 years of faffing with bikes, every day's a
schoolday.

 

I thought that may be involved, but thought it was so bizarre and
ridiculous, I risked looking a bit foolish if posted....

 

It's never stopped you before ;-)