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FrankenDesmo · 10-03-2020, 07:57 AM

I got it back together on Sunday night, then realised my new socket sets didn't come with plug sockets, nor the correct size deep socket for the NGK plugs (18mm - the Denso ones already in it were 16mm, which I also didn't have, though a 17mm did the job to remove them

).

So got hold of an 18mm plug wrench yesterday (couldn't find a socket locally, just a whole one-piece wrench

), and put the new NGKs in. Noticed that the Densos were the equivalent of an '8' on the heat scale and the new ones are '9' (stock), so I've gone a grade colder by the looks. No idea what the implication will be, but perhaps a hotter plug is needed up here in the cold, dark north

.

I plugged up the vacuum port where the scottoiler was connected as best I could (snipped a bit of the scottoiler line, jammed a bit of ~1mm wire up it, jammed it into the L-piece and put some heatshrink over the whole thing.

Bike started up a lot nicer (new plugs & air filter - go figure). All seemed well until it warmed up, then the revs went back to 2.5-3k

I tried spraying some WD40 around the inlet runners to see if there was any change, there wasn't anything perceptable. Removing the makeshift plug off the vacuum nipple caused no change, and even holding my finger over the nipple hole only dropped the revs by maybe 500, down closer to 2k.

I also noticed that the exhaust pulses from the front cylinder were not as 'smooth' as those from the top, and this seemed to be the only cylinder that was missing/hesitating. Revving the bike with my hand close to each exhaust the top cylinder was smooth & strong, but the front was very 'lumpy'. The bike stinks of unburnt petrol while running, too, so I don't know if the front cylinder is running rich, and the top lean (as the old sparkplugs seemed to indicate), which is making the front rough but the top seem OK.

I wasn't able to ride it out as I needed to hang around home waiting for a plumber, and it was bucketing down outside. This afternoon I'm going to take it for a quick, hard ride just in case that helps at all (I've got some injector cleaner in the fuel).

Otherwise I'm picking up a long screwdriver and waiting for the carbtune to turn up (and vacuum nipples with new seals and proper caps), then I'll check/adjust the sync. With the mixture screws, the advice seems to be to screw one in all the way, noting how many turns, and setting the other to the same - in my case I'm not sure which cylinder to use as a baseline as top "seems" to be running OK, but that could be because it's running lean?

What about the idle speed screw, should I be messing with that at all? The bike does seem to have had a slightly higher idle the whole time I've had it, which points to the problem that I've never actually had a solid baseline on this bike - I'm effectively sorting out niggles from it being stored for several years (the previous owner purchased it and had it running, changed the belts & oil, but it's always had at least a small hesitation and the idle not quite right, based on the brief amount of time I was riding it after buying it).

Arg, more questions than answers!

10-03-2020, 07:57 AM	#45
FrankenDesmo Member Join Date: Sep 2019 Location: Glasgow Bike: M900 Posts: 108	I got it back together on Sunday night, then realised my new socket sets didn't come with plug sockets, nor the correct size deep socket for the NGK plugs (18mm - the Denso ones already in it were 16mm, which I also didn't have, though a 17mm did the job to remove them ). So got hold of an 18mm plug wrench yesterday (couldn't find a socket locally, just a whole one-piece wrench ), and put the new NGKs in. Noticed that the Densos were the equivalent of an '8' on the heat scale and the new ones are '9' (stock), so I've gone a grade colder by the looks. No idea what the implication will be, but perhaps a hotter plug is needed up here in the cold, dark north . I plugged up the vacuum port where the scottoiler was connected as best I could (snipped a bit of the scottoiler line, jammed a bit of ~1mm wire up it, jammed it into the L-piece and put some heatshrink over the whole thing. Bike started up a lot nicer (new plugs & air filter - go figure). All seemed well until it warmed up, then the revs went back to 2.5-3k I tried spraying some WD40 around the inlet runners to see if there was any change, there wasn't anything perceptable. Removing the makeshift plug off the vacuum nipple caused no change, and even holding my finger over the nipple hole only dropped the revs by maybe 500, down closer to 2k. I also noticed that the exhaust pulses from the front cylinder were not as 'smooth' as those from the top, and this seemed to be the only cylinder that was missing/hesitating. Revving the bike with my hand close to each exhaust the top cylinder was smooth & strong, but the front was very 'lumpy'. The bike stinks of unburnt petrol while running, too, so I don't know if the front cylinder is running rich, and the top lean (as the old sparkplugs seemed to indicate), which is making the front rough but the top seem OK. I wasn't able to ride it out as I needed to hang around home waiting for a plumber, and it was bucketing down outside. This afternoon I'm going to take it for a quick, hard ride just in case that helps at all (I've got some injector cleaner in the fuel). Otherwise I'm picking up a long screwdriver and waiting for the carbtune to turn up (and vacuum nipples with new seals and proper caps), then I'll check/adjust the sync. With the mixture screws, the advice seems to be to screw one in all the way, noting how many turns, and setting the other to the same - in my case I'm not sure which cylinder to use as a baseline as top "seems" to be running OK, but that could be because it's running lean? What about the idle speed screw, should I be messing with that at all? The bike does seem to have had a slightly higher idle the whole time I've had it, which points to the problem that I've never actually had a solid baseline on this bike - I'm effectively sorting out niggles from it being stored for several years (the previous owner purchased it and had it running, changed the belts & oil, but it's always had at least a small hesitation and the idle not quite right, based on the brief amount of time I was riding it after buying it). Arg, more questions than answers! Last edited by FrankenDesmo; 10-03-2020 at 08:19 AM..