Kiwi Rider
Registered
A guy I know asked me to have a look at his '91 GSF250 Bandit that he had just acquired.
When he was on the way home from the seller's place, the bike crapped out and he had to call his missus to come pick him up with the car and trailer.
He told me it was running really poorly, with a lot of surging and misfiring.
I took it home on my trailer and that was back in July of this year . . . I know . . but he said he was in no hurry for it and wished he'd never bought the thing, impulsive decision I'm thinking lol.
After a few hours of checking it over I came to the conclusion the compression was way too low to allow a proper combustion, consequently fouling the plugs and it was near impossible to start without a jump battery or a push start.
Compression test showed it only had 50-60 psi in each cylinder.
Soooooo . . . . over the next few months I picked away at it and here is what I did . .
I checked all valve clearances (shim under bucket) amd they all had clearance, I checked cam timing, all ok.
I did a leakdown test and it had leakage into the crankcase, valves appeared to be holding pressure.
I stripped the engine top end and measured the pistons, ok
the ring gap in the bores, excessive at .025", the max is .012". (min is .008")
the piston to bore clearance, ok
the bore ovality and wear, all within .002" so all ok.
The bores were glazed pretty bad so I gave them a decent hone, replaced the rings, fitted new base gasket and head gasket, had the cylinder head stripped and surfaced, .002" machined off it, checked all the valves and seats, all looked ok, reassembled and set all valve clearances to spec.
Rechecked the compressions . . . wow! all around 200 to 210psi !!!
I then stripped the carbs and the pilot jets were quite blocked, the needles were set incorrectly, so I set them back to standard position, circlip in the middle recess. The mixture screws were seized on 2 carbs, I freed them up and replaced the little o-rings and washers sealing the mixture screws in their seats. (2 were missing altogether!)
I replaced the needle and seat o-rings and set the float heights to the correct height.
Checked the main jet size and condition, and also the starter jets (choke circuit), they were ok.
Fitted new spark plugs, oil and filter changed, and cranked it over.
She smoked a bit on start up for a few minutes, then cleared and ran quite nice.
I also stripped and cleaned the calipers front and rear, replaced front pads, new brake fluid,
stripped and cleaned the forks, new seals,
cleaned, lubed and adjusted the chain,
went through all the electrics and cleaned all the main connections, charged and tested the battery, that was ok.
I gave the bike a thorough going over, and corrected a lot of issues caused by people fiddling with it and not knowing what the heck they were doing.
Anyway, here's a short vid of a cold start up, it's 18CdegC so not that cold lol.
I'm pretty chuffed at the result, but I don'yt know how the owner is going to react when he sees the bill . .
$550 in parts and $500 in labour.
I actually spent a lot of time on it, maybe 40 hours, but it was a bit of fun for me just working in my own space, and at my own pace, no pressure at all.
When he was on the way home from the seller's place, the bike crapped out and he had to call his missus to come pick him up with the car and trailer.
He told me it was running really poorly, with a lot of surging and misfiring.
I took it home on my trailer and that was back in July of this year . . . I know . . but he said he was in no hurry for it and wished he'd never bought the thing, impulsive decision I'm thinking lol.
After a few hours of checking it over I came to the conclusion the compression was way too low to allow a proper combustion, consequently fouling the plugs and it was near impossible to start without a jump battery or a push start.
Compression test showed it only had 50-60 psi in each cylinder.
Soooooo . . . . over the next few months I picked away at it and here is what I did . .
I checked all valve clearances (shim under bucket) amd they all had clearance, I checked cam timing, all ok.
I did a leakdown test and it had leakage into the crankcase, valves appeared to be holding pressure.
I stripped the engine top end and measured the pistons, ok
the ring gap in the bores, excessive at .025", the max is .012". (min is .008")
the piston to bore clearance, ok
the bore ovality and wear, all within .002" so all ok.
The bores were glazed pretty bad so I gave them a decent hone, replaced the rings, fitted new base gasket and head gasket, had the cylinder head stripped and surfaced, .002" machined off it, checked all the valves and seats, all looked ok, reassembled and set all valve clearances to spec.
Rechecked the compressions . . . wow! all around 200 to 210psi !!!
I then stripped the carbs and the pilot jets were quite blocked, the needles were set incorrectly, so I set them back to standard position, circlip in the middle recess. The mixture screws were seized on 2 carbs, I freed them up and replaced the little o-rings and washers sealing the mixture screws in their seats. (2 were missing altogether!)
I replaced the needle and seat o-rings and set the float heights to the correct height.
Checked the main jet size and condition, and also the starter jets (choke circuit), they were ok.
Fitted new spark plugs, oil and filter changed, and cranked it over.
She smoked a bit on start up for a few minutes, then cleared and ran quite nice.
I also stripped and cleaned the calipers front and rear, replaced front pads, new brake fluid,
stripped and cleaned the forks, new seals,
cleaned, lubed and adjusted the chain,
went through all the electrics and cleaned all the main connections, charged and tested the battery, that was ok.
I gave the bike a thorough going over, and corrected a lot of issues caused by people fiddling with it and not knowing what the heck they were doing.
Anyway, here's a short vid of a cold start up, it's 18CdegC so not that cold lol.
I'm pretty chuffed at the result, but I don'yt know how the owner is going to react when he sees the bill . .
$550 in parts and $500 in labour.
I actually spent a lot of time on it, maybe 40 hours, but it was a bit of fun for me just working in my own space, and at my own pace, no pressure at all.
