pop-pop-burble-pop-burble-burble-pop

Is roughly what the Raptor's rear cylinder's doing at idle, compared to
the perfect pop-pop-pop-pop-pop of the front cylinder. Open the
throttle a bit & it's fine.

I've put new plugs in, done the valve clearances (which were within
spec but towards the tight end, so I re-shimmed them to the slack end),
set the TPS, checked the air bypass screws, balanced the TBs & cleaned
all the loom connectors. There's no sign of an air leak anywhere
(either intake or exhaust).

I'm not particularly fussed about it other than the perfectionist in me
wanted it sorted. Likely causes, or is it a case of 'they all do that
sir'?

 

I know you say there are no air leaks, but does it burble or bang at all
on the over run?

Otherwise I can't think of anything except a slightly dodgy HT lead
shorting out on something.

Or a very, very slightly 'burnt' valve (seeing as the clearances were a
smidgen tight. Unlikely though if it starts and goes well otherwise.

Do they set up the mapping to run the rear pot a tiny bit richer than
the front, or am I harking back to the bad old days of air cooled narrow
angle V twins?

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

 

No not at all. Leaving a vacuum port open on the front cylinder just
makes the revs go up a bit anyway, it still carries on with its perfect
pop-pop-pop.

It's a thought. The leads & caps look in perfect nick, but I'll check
it tonight when it's dark.

Don't think so. It runs perfectly just off idle & above, & the tightest
valve was still 0.03 above the lowest limit.

Some of the modern Triumphs have a richer centre pot too. But I've not
seen that mentioned anywhere about Raptors/TLs. I'll hopefully be
getting the PC mapped this week so I should find out then.

Actually you've just given me a thought. I'm now wondering if they run
a different map at idle (they certainly do when the clutch switch is
engaged), & the TRE is confusing it. Some people on the Raptor forum
have complained about much jerkiness when crawling in traffic with a
TRE fitted, which would kinda back that up if the rear cylinder's
running unevenly. I can switch my TRE on & off so that's easy to check.

 

Not what my TLR ever did. If you hadn't said 'no exhaust leaks' then
that would've been my diagnosis. The TL rear pipe is in two bits that
clamp together; on mine the gasket had disintegrated, leaving just a
wire basket.