G5 - First Serious Ride

[starfield181]

Thought you might like a report on my G5 which I took for its first longish run to a club meeting today; about 20 miles each way. Not totally successful but at least it got me there and back again and was a sweet ride during the times when it was running properly. Initial observations were that the front brake is not overly effective but adequate so any attention to this area can go on the back burner. The front forks seemed a bit hard so I will drain and refill with some fresh oil (no idea what's in there at present). Also it seems to be very low geared, flies up hills but could do with a 5th gear as an overdrive for the flatter bits. Clutch though still heavy works well and the gearchange is smooth with just a trace of whine in 2nd & 3rd. Bit more vibration than I was expecting but not a major issue and on the (very) odd occasion I ventured over 55 it was if anything less noticeable. Plenty enough power for my needs once I can use it – see below.

Lots of hopefully little jobs to do in no particular order.

Oil leak from nearside with some oil on tyre so gearbox oil seal or breather are obvious suspects. Oil still leaking from k/s spindle (awaiting seals) but even so the level did not drop much over the 40 miles and the primary chaincase is still right up to the mark. However, the engine oil level dropped maybe 3/8” though it does not smoke nor are there any obvious leaks from this source so it may be coming out of the breather. Don't regard any of these as show stoppers for the moment and I have it in mind to fit a larger gearbox sprocket and will replace the gearbox oil seal at the same time if it needs it.

Plug was a little lighter shade of brown that I would have liked but this is most likely my fault as I dropped the needle one notch when investigating the apparent rich running. Plug gap was 32thou but both these items are easily remedied.

Biggest issue was a misfire. It could occur at any speed and was difficult to pin down but seemed to worse on larger throttle openings but equally could happen at low revs and light throttle. I will check over the fuel system as it could be dirt in the carb. However, my gut feeling is it's electrical and very likely something simple like a loose connection. I will swap out the coil and the condenser as I have spares for both but since it did not get noticeably worse when the engine got hotter I somehow doubt its either of these; there was only minimal occasional arcing at the points. I'll leave a new set of points as the last option as they are particularly cheap.

So overall about what you might expect from a first run on a bike that has not been on the road since 1995.

PeterF

[56G80S]

Misfire on the overrun or when throttle applied?

Johnny B

[Stuoyb]

For the gearbox oil leaks, apart from the main seal look out for weepage on the threads where the selector shaft screws in and leaking from the core plugs behind the shaft bushes.
Both are easily remedied, selector shaft threads - fit a grub screw with some sealer.
With the core plugs, clean the area around them and cover with araldite.

[starfield181]

Misfire on the overrun or when throttle applied?

Very occasional misfire on the overrun which actually seemed to go away later. I would say that 99% of the time the misfire was when throttle was applied.

Just in case it turned out to be a terminal failure, I asked a friend to follow me home. He observed that when it misfired at relatively slow speeds what he saw from the exhaust was black smoke, when I was giving it a bit more stick there were flames coming from the exhaust. When it was not misfiring, the exhaust was quite clean. It was as much this observation that convinced both of us it was probably an ignition rather than carb fault. The theory being that when it misfired (perhaps cut out might be a more accurate description) unburnt fuel went into the exhaust system either being blown out as smoke or flames depending on whether it ignited or not. Of course we could be totally wrong.


PeterF

[Ozmadman]

Most lightweight owners complain about the under gearing which for me virtually made first gear irrelevant, you should have an 18 tooth sprocket as standard fitment on a G5. I have tried a 19 and a 20 and find the 20 tooth ideal, 1st gear becomes useful again and 60 mph is far more comfortable for bike and rider. The only drawback if you can call it that, is that you will probably need to change down if you drop below 30mph in top so probably a 19 would be better if you only ride around town.

3rd gear whine seems to be pretty standard and both of my boxes which have been rebuilt and showing no apparent wear whine a bit in third, even more reason to keep that oil topped right up.

The misfire could be ignition too far retarded causing fuel to ignite in the front pipe, I had this with mine when I first got it causing my front pipe to go blue before my eyes!!! Timing is 1/4"BTDC with the adv/rtd unit set(wedged open) to full advance with the points (12 to 14 thou)just opening

[starfield181]

Thanks Paul,

Reassuring about the gearbox whine and based on the previous comments about gearing I was planning to swap my gearbox sprocket for a 20t which will give me a chance to check and replace the output shaft oil seal if that is showing signs of leakage.

The misfire could be ignition too far retarded causing fuel to ignite in the front pipe, I had this with mine when I first got it causing my front pipe to go blue before my eyes!!! Timing is 1/4"BTDC with the adv/rtd unit set(wedged open) to full advance with the points (12 to 14 thou)just opening

I will double check the ign timing as I do get the feeling that it is not quite right. The effect my friend observed of flames appearing in the exhaust is consistent with fuel being burnt in the exhaust system though until you mentioned it, I would not have thought about it being caused by retarded ign.

Not yet had time to start the investigation - SWMBO has a few other priorities for me.

Peter

[starfield181]

Quick update. I raised the needle one notch to richen up the mid/top range mixture bit. While the carb was off I checked the flange on the carb manifold and O ring, both fine. The correct thick heat gasket is fine and I replaced the paper gasket and used a smear of Wellseal both sides just to make sure. On the ignition side I checked the timing but once I had cleaned the points and set the gap to 15thou it seemed to be pretty much spot on. The points seemed clean enough anyway and look new with plenty of spring tension. Running the engine the points did seem to be sparking a lot so I fitted a new condenser which seemed to cure that problem.

Anxious not to change too many things at the same time I took it for 4-5 mile test ride today and it pulled 50 easily up the hills without any trace of misfire. so far so good. However two things have re-emerged which require more investigation; I doubt they had gone away, just masked by the misfire. The problem of hesitation when running on a light throttle has come back, not so much a misfire a a sort of surging or hesitation. Also and I think its connected, a reasonable tickover can only be achieved with pilot air screw adjuster screwed well in; anything more than 3/4 turn out and it dies quickly. In fact even when you have a good tickover, it eventually slows and stops. Don't think its ignition related this time as I tried advancing and retarding the points plate from what I believe to be the correct timing position. It had no obvious effect on tickover reliability either way so I reset the timing.

Decided at that point it was best to retire to the keyboard with a cup of tea hoping inspiration would strike. `
Are we downhearted - course not.

PeterF

[SPRIDDLER]

(Me again. Too much time on my hand )

Excellent progress.
I think you could be needing to reduce the air supply to the pilot jet by screwing the screw inwards more than usual because the pilot jet or the drilling in the carb body is partially blocked. Remove and check that the tiny hole at the end of the jet and the two holes at the side are clear. Poke a wire brush strand through to make sure.
If the carb body drilling is partially blocked you'll have to try forcing aerosol powered WD40 or carb cleaner through.
An over-rich pilot setting can cause hesitance/surging at small throttle openings.

[starfield181]

I think you could be needing to reduce the air supply to the pilot jet by screwing the screw inwards more than usual because the pilot jet or the drilling in the carb body is partially blocked. Remove and check that the tiny hole at the end of the jet and the two holes at the side are clear. Poke a wire brush strand through to make sure.
If the carb body drilling is partially blocked you'll have to try forcing aerosol powered WD40 or carb cleaner through.

Good diagnosis and I had the same thought. Just come back in from the garage having cleaned a blocked pilot jet. The fuel in the base nut of the monobloc was quite cloudy so it looks like I need to clean the tank out and fit an in-line filter otherwise this problem is going to recurr. I was only able to run the engine briefly in the garage last night but the signs were good. Needs a run to get thoroughly warmed up and the carb re-setting now.

The seals and gaskets for the leaky gearbox end cover have arrived so girding my loins for that job next.

PeterF

[starfield181]

As reported elsewhere, with forum help I have sorted the major oil leak from the k/s spindle. I took the bike for a 20 mile ride today as the sun was shining. Bike is now oil tight on the RH side. Some drips from the LH side, I suspect it will be the gearbox mainshaft oil seal but I can live with these until I am ready to upgrade the gearbox sprocket. This won't be long as the bike does feel desperately undergeared rarely needing to drop to 3rd even around town

The hesitation under light loads has gone away but the tickover is still a little erratic and I have popping and banging in the silencer on the overrrun. I imagine they are connected but not sure how. I will be re-checking the timing and the seal between exhaust pipe and head. This seems to be a push fit so not sure yet what I can do about this. I have already checked to make sure there are no leaks on the carb/manifold side.

Anything else I should check?

PeterF