1990 GSF250 Bandit Make Over and Tune Up . . . My Therapy !

[Kiwi Rider]

I was getting a bit tired of sitting in front of the computer, watching you tube vids and docos, and I've been avoiding going out and spending money, plus it's winter here so . . . . . the other day at work a bloke I've never met drops into work and asks for me.
Turned out he worked with my old workmate ( an excellent Subaru and Toyota technician), and my buddy had given him my number as a possible lead to fix his new (to him) bike he had just bought.
It's a little 1990 Bandit 250 which he got to commute on, and on the ride home from picking it up, it broke down.
So anyway . . he's a really nice guy, 65 and just retiring from full time mechanic duties, but not confident on working on bikes, just rides a bit.
I picked it up on my trailer and brought it back to my cave and started assessing the problems it has.
The rear axle was loose as a goose, the front brake was spongy with air, the fork seals leaking like a siv, the rear brake hose banjo bolts loose, and that was just the safety check items!
I moved on to the poor running issue, removed the plugs, removed the airfilter and airbox, removed the carbs and took a few pics of what I found . . . .
Here's the bike . .

air filter . .

This is how I found the throttle tube . . . somebody's had a play . .

Carbs . . .

I had little Jimi helping and even he was shocked at the poor condition of the bike!!

Next step is a compression test, if it's OK on compression I'll go ahead and sort the carbs out, if comps are low, I'll do a leak down test to see whether it has tight valve clearances or worn rings.
Will keep you informed. Kiwi

 

[john blaze]

Whoa, Totally shod hey.

 

[john blaze]

Like the doggy.

 

[Kiwi Rider]

Like the doggy.

That's my youngest son, he's 10, the oldest boy is 14 and GRUMPY!
Jack Russell/Bichon cross.
Yeah, it's no biggie really, it's just been neglected for a long time, then some old guy that owned it and knows feck-all about mechanical literacy had a wee play with things,
the bloke that bought it was assured it was 'all good to go', yeah right.
Just lucky he found me and I'm a nice guy, just like he is lol.

 

[Kiwi Rider]

They are funny wee bikes to ride, no power at all until 10,000rpm, then a little kick in the bum thru to 16,000rpm.
Pistons are the size of cotton reels with a short stroke, no torque at the crankshaft let alone at the rear wheel . . . gear selection is crucial!!

 

[Kiwi Rider]

So I've cleaned everything up, compression tested and leak down tested it, the compressions were around 50 psi cold, and warmed up around 100psi on No 1 and No 3, but No 2 and No 4 are low at 85psi each.
The spec is min 135psi and a healthy motor has 165psi.
The Leakdown test revealed leakage between No 1 and No 2 cyls, across the headgasket by the looks of it, I checked all valve clearances and all within spec clearances.
After cleaning all the jets and setting the float levels (they were all too low), fitting new needle and seat o-rings, and raising the jet needle 1 notch back to standard position, setting the mixture screws at 2 turns out, I refitted the carbs.
It was a marked improvement on the cold starting and now idles really well at 1500rpm (that's the spec) when warmed up but it took a bit of mucking around with the pilot jet mixture screws to find the happy spot for idle vs cold starting.
Obviously the low compression is the cause of hard starting (it's not ideal, but better than it was), it's the low vacuum not drawing the fuel through quickly or adequately enough.
I've replaced the fork seals and added fresh 10 weight fork oil.
Replaced that dodgy throttle tube with a new OEM part.
So far so good . . . .

 

[Bumblebee]

Great that you are playing with the wee beastie...I don't know how I missed the original thread...