Keeping my S2R 800 going and healthy. Winter small things, again ...

[koko64]

As long as it's not caused by valve clearance/valve/valve seat issues, then it might be time for that high compression, big bore kit. There might be cylinder bore "ovality" too. Sometimes the pistons ring grooves peen over holding the rings inwards and stopping the rings from sealing. Saw this recently on a high mileage, high compression M750 and also an SB6. The M750 big end was giving way and the rings had to do the job of stabilizing the piston and conrod. It didnt like it! This caused excessive piston blow by. The symptom was high oil vapour from the crankcase breather, low compression and big end noise. On the SB6 the cause was bad fuel contamination of the oil and high revs. The symptom was smokey exhaust when hot.

[stopintime]

New cylinders two years ago (big bore, 88 to 90). New pistons one year ago, but burned and were replaced by my old and worn pistons (Pistal HC). Will replace them soon.

I would expect some compression loss, but have no idea how much it takes to mess up the running like mine is.

Anyone know how different the results might be, testing with open throttle? Most online DIY advice is to use WOT, but the Workshop Manual doesn't mention it. Anyway, I didn't know, so closed throttle during my tests. Significant?

[ducpainter]

New cylinders two years ago (big bore, 88 to 90). New pistons one year ago, but burned and were replaced by my old and worn pistons (Pistal HC). Will replace them soon.

I would expect some compression loss, but have no idea how much it takes to mess up the running like mine is.

Anyone know how different the results might be, testing with open throttle? Most online DIY advice is to use WOT, but the Workshop Manual doesn't mention it. Anyway, I didn't know, so closed throttle during my tests. Significant?

Yes...significantly different. Compression test with WOT, otherwise there's nothing to compress.

[stopintime]

Yes...significantly different. Compression test with WOT, otherwise there's nothing to compress.

Thanks, I will try again. I thought maybe it would 'inhale' through the butterflies which are always a little open... or through the exhaust valves for that matter. Not a lot of flow going on at the speed we're using here?

[stopintime]

Yes...significantly different. Compression test with WOT, otherwise there's nothing to compress.

significantly higher or lower?

[ducpainter]

You should see significantly higher numbers.

[koko64]

I reckon in the 180 + psi range. WOT and hot motor. Keep cranking until the needle stops.

[Howie]

Also mild cams higher numbers, hot cams lower numbers.

[koko64]

Yes, true. 

[stopintime]

Ok - new test, proper warm engine and WOT.

(I tried with the rubber cone and besides an attempt to spit it out, it was ok. Would like to have had three hands, but ok)

Same result on both. Lower.

Biggelaar is happy to more or less rule out big mechanical problems. Switch coils is next. One exhaust was cold when I let it run on one cylinder. If the other is cold after a switch, we just might be closer.

[stopintime]

The coil switch didn't make any difference. Rear cylinder, measured infrared on the exhaust pipes, is half the heat of the front. This is at 2-2,500 revs, idle lever pulled, which sounds like it makes the bike go on one and a half cylinder.

I feel a little lost, but will soon enough move down the list.

[MonsterHPD]

This sounds exactly like what happened when I got the cam belt on one tooth wrong. I don't remember in which direction , but one way the piston and valves will hit, in the other direction the motor will run, but sluggish and with a cold(ish)  header on the affected cylinder.
In my case it was on the m900 with Veetwo cams, but I assume it would / could be the same on an 800 with st2(?) cams.

[stopintime]

^^

hmm... that's interesting because at this point I'm curious about / leaning towards a mix of several small things and a-tooth-off could fall into that category. However, that kind of bad running wouldn't become worse over time? Another "however" is that it ran smoothly'ish going into this summer's Dyno work and quite poorly when leaving the workshop after excellent test results.

It's really difficult to ignore the very clear difference between JUST before and JUST after the Dyno work.

It became better after an ECU adjustment, but still far from good.

Either a mix of several small things not discovered during tuning OR that one big thing we still haven't found / thought about.

Biggelaar wants lamda measurements to see what his adjustments did. Maybe they were correct, but not sufficient....

I'm going to see if I can clean the intake, around the butterflies. The autumn water ingress could easily do nasty things....


I'm not very optimistic about this riding season, but will keep working towards a great result.

[MonsterHPD]

Well, if it has changed without the belts beeing off, then a "tooth off" situation is not very likely .... but the symptoms are really VERY similiar: sluggish, cold heaer, running lime "on a cylinder and half ...". Maybe a quick check of the cam timing on that cylinder just to make sure nothing has worked lose.

[stopintime]

Thanks - work in progress.

Just a shot in the dark really, maybe the inlet should be cleaned? They have been left untouched for all of the 240.000km and the place they get most dirty is where the butterflies usually are - I now know that at least 90% of my riding is very close to 15 degrees. This theory corresponds well with the dirt I could see. I used brake cleaner, WD40 and carb cleaner

It helped!

Not perfect, but substantially better. Now it's a little annoying where it yesterday was difficult to ride (at least in town).

Since I now don't have any main suspects, I try to focus on how many and which of the small things it can be. Dirty inlet was one. Still is actually. I'm buying another spray can of carb cleaner - maybe there is more nastinesses in the valve area... Of course fuel filter is still on the list. Both because Howie suggested it and because I really can't NOT try a new filter.