Suzuki GP100 bogging at Full Throttle

[Steve_W]

[Steve_W]

evening all....

Just thought I'd popst an update from the work over weekend.

Swapped to a lower main jet, which made no difference whatsoever, so I have put the original main jet back in. Took exhaust off and checked it and I am pretty sure there is no blockage.

I'm going to have to bite the bullet and change the stator plate and see if that is my issue I think.

Aside from that I guess I'll need to look deeper and do a compression test to check for worn rings or worse

Does anyone have anything good to say about the "budget" compression testers you can buy from ebay or amazon?

[Nobby the Bastard]

I don't see what replacing the stator plate will do to help. GPs have points, and not cdi and so doesn't have a high and low speed coils.
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trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Sprint ST 1050

[redeem ouzzer]

[Nobby the Bastard]

If it were the stator it would be not working all the time. I'd be looking to see if it has a broken advance (if it has one, it was a long time ago I had one so can't remember.)
____________________
trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Sprint ST 1050

[Steve_W]

from what I can gather, it has fixed timing, no advance/retard.

As for what powers the points and ignition coil, again from what I can work out and from reading the manual with my (very limited) mechanical knowledge is that the stator has two coils, one for the lights (headlight and tail light only work when engine is running) and the other is for charging the battery and I assume providing power to the points, ignition coil etc? The battery isn't needed for the bike to run, all the battery does is power brake light, indicators, neutral light and horn (I think).

Could it be this "charging" coil breaking down under load?

[Nobby the Bastard]

[Steve_W]

How hot is "hot" before it's likely to start breaking down?

I only ask because when I changed the main jet at the weekend and took it for a quick run, I initially thought I had fixed it because it felt like it was pulling better as I set off, but as soon as I got off my estate and onto the main road it was being a twat again

[Nobby the Bastard]

When they break down they fail completely until they cool down again, which would take about half an hour.

It would be miraculous if it was your stator plate coil at fault simply because its failing on a given throttle position.
____________________
trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Sprint ST 1050

[Sister Sledge]

Quick question: Are the points new? They wear out and as well as the gap changing, the actual electrical contact surface becomes hitty missy.
Have you replaced the points (cheap!) and set the gap correctly?
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CCM 404 DS

[Nobby the Bastard]

I'm actually wondering if the points are in the correct position to set the timing right.
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trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Sprint ST 1050

[Steve_W]

The points are not new, when I took the bike in for the carb to be cleaned, they also checked the timing and said it was spot on.

As mentioned, they are not new points, but Bike shop said "they're OK" and the way he said OK I interpreted it to be "not completely buggered but not in A1 condition".

I do have a new set of Genuine Suzuki points that I was going to fit to the used stator I have bought and was also going to fit the new condenser I bought that is currently on my existing stator.

Nobby, not sure what you mean about points being in correct position if the timing has been confirmed as OK?

[A100man]

[Steve_W]

I think I might change the points but leave the original stator in there for now?

I've also ordered a carburettor repair kit, which means I can eliminate a worn jet needle etc as well.

I probably won't have much time to do this until the weekend, but will update as and when I do each thing with my results.

Once again, thanks for all your help you lovely people

[Sister Sledge]

The points cam lobe will likely have a lubrication felt pad somewhere? My old Yamahas used to. If it's not looked after it dries or the oil goes hard on it and the contact part of the points wears as has been mentioned.

You know what? I reckon new points will fix this. It's easy peasy to replace them - follow instructions fully though because you could damage the taper on the crank and that's bad!
Replace the points and report back. I'd avoid stators for now and just do easy bits.
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CCM 404 DS

[Steve_W]

[A100man]

[Sister Sledge]

Yup. Damage to the crank is incredibly easy to do - knocked threads or bent shaft.
Mind you - they're wanting to replace the stator so it's coming off regardless.
I'm not familiar with the GP100 - was it a small threaded puller? Must be easy to get one if they don't have a decent puller set.
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CCM 404 DS

[Steve_W]

first thing I bought when I realised I had a problem that could be electrical was the right size flywheel puller

The hardest part of removing the magneto flywheel when we changed the condenser was undoing the nut that holds it on! Using the flywheel puller made removing the flywheel a piece of cake

[Steve_W]

Quick update on this as I'm still suffering the same problems, although maybe my initial description could have been a bit misleading as it's not exactly correct......

I have now replaced all electrical parts of the ingition:-

ignition coil and HT lead
replaced stator with used ebay purchase
new condenser
new genuine Suzuki points
new spark plug ( I've bought 4 more so once it's finally running properly I can do plug chops to ensure mixture is correct etc.)

Compression tested and that seems absolutely fine.
Exhaust is not blocked as far as I can tell.

Timing is set correctly to 1.87mm BTDC (used a gauge to find TDC and 1.87mm before TDC) and proved points opening at correct time with multimeter. Points gapped correctly also.

Took bike out for short run. picks up niceley at 1/3 throttle and will rev all the way up the rev range as far as I could until the road ran out!

As soon as I open throttle much more than that when trying to accelerate it dies (bogs?) as it always has done.

So.......

I took air filter out and ran it up the road (each "test" run was only around a mile to avoid causing damage due to being too lean etc). No difference.

Took airbox off completely and ran it. Was improved but not 100%.

Took carb cover off and ran it up the road. Massive difference. Pulled all the way to 8k before it started to struggle - I'm guessing due to it then being too lean at that point due to TOO much air?

So I think this kind of proves to me that it has to be fuel related after all, and that it is far too rich at certain points in the rev range?

[Steve_W]

I have a carburetor repair kit that I bought from wemoto, so I am going to start looking at doing that next, but take a look at the needle that is supplied in the kit compared to the one that is currently on the bike......

https://i.ibb.co/sHzRvYJ/jet-needles.jpg

Now either the original (on the left) is VERY worn, or the new one (on the right) is fecking massive!!!!

I might just try moving the clip up each notch on original needle first as it's a quick easy job, just to see if it helps. it's in the middle at the moment, so I can lean it off by two notches on original needle anyway. Guess it's worth a try,

[Nobby the Bastard]

You can see where the original is worn because thge gold anodising has been worn off.

The new needle is a totally different shape so I would expect the kit to contain a new emulsion tube as well.
____________________
trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Sprint ST 1050

[Steve_W]

There's no emulsion tube in the kit, so I guess that needle is next to useless for me really

This is what came in the kit:-

https://i.ibb.co/wh17WrP/carb-kit.jpg

I am going to have a play with the original needle first anyway, just to see if that makes any difference, but failing that I guess I'll need to try and find an original needle from somewhere.

There are actually a couple of old threads on BCF with people having exactly the same issue as I am having, also with GP100s, but annoyingly there is no resolution!

Buy an old bike they said, it'll be fun they said......

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[Steve_W]