My GK76a winter service/tidy-up project.

[wullie3xv9]

Thanks Donk though it's looking better in the pictures than it does in the flesh ! The replacement L/H belly panel has had the 3 Dzus receptacles pop riveted on & the panel's been fitted along with the little V piece so the service/tidy-up is now officially finished. It's now cleaner, tidier &, most importantly, mechanically A1.

I just need some free-time & dry, sunny weather now to give it a run out & see how she feels.

[wullie3xv9]

Hi folks, time for an update. As I was off work last Tuesday ( the 10th ) & it was a cool but sunny day ( +8 Deg. C ), I took my 76a into a local MOT testing station. I'm chuffed to report it passed first time with no advisories.
When I got home I went on-line & taxed it then, after some lunch, went out again & put some more miles on it.
By the end of the afternoon I'd done a total of 123 Kms/ 76 miles during the day with no major problems surfacing.

Here's the auld git at home after an afternoon of ... ehm ... fun.


The only gripes are that the carburation is a bit rich around 3,500 rpm causing the engine to stutter. The warmer the engine gets the worse it gets. I've progressively leaned off the mixture screws & they're now set at one full turn out, (from 2.75 turns out), which is as lean as I can go or else the engine is reluctant to idle or start!
Mr VVS's advice earlier in the thread that the stock 47.5 pilot jets might be OK with the mixture screws set at around 3 turns out instead of 1.5 might be the way to go after all...

Above the stutter though, when the motor gets to 4,000 it's off! Between 4 & 6 thou. it pulls strongly for a short stroke 400 4 stroke. Short shifting through the gearbox, (which is sweet as a nut by the way), it's up through the gears to sixth like a moto-crosser, & that's with higher 15/44 final gearing fitted! Between 6 & 8 thou. it flattens off a bit but pulls progressively harder from 8 thou up 12 thou. ish. (The needle clips are currently set in their 4th from top slots). It accelerates fine in top gear between 6-8 thou. rpm so don't think it's too weak or rich. Maybe the way the Sandy Bike Spares stainless downpipes work?? With the higher final gearing it's indicating 102-103 Kms @ 6,000 rpm & 162-163 Kms @ 10,000 rpm.

The only other gripe is that even with an SV 650 82 degree C thermostat fitted the temp. needle is still only just into the white NORMAL zone, but this could be 'cause the fuelling is on the rich side helping the engine to run cooler than optimum. So ... I may yet have to fit an 86-88 deg.C thermostat from a CBR 600. I live in the "Frozen North" after all.

I forgot to mention during the rebuild that I slotted the mounting holes for the ignition trigger in the L/H engine cover so the ignition timing has been advanced 3-4 degrees, maybe a bit more ?? Advancing the timing worked a treat on my 3XV so thought why the hell not ... I did see it mentioned a couple of times when reading through old GSXR threads .

Next time I'm off & have good weather I need to try a "plug chop" type run to see if the 117.5 main jets are too rich, too weak, or spot on, changing them if needed & then checking/adjusting the needle settings. Once they're established I'll whip the carb's off ... again ... & swap the 52.5 pilot jets for the stock 47.5's & also fit the set of LiteTek internal carb o-rings & seals I bought. Once I'm happier with how it's running from idle to high up I'll book it into the local Dynajet centre & get the auld git checked out properly.

When I remember, the mixture screw on No.1 cylinders carb is now set the same as the other three carb's !
What ever was causing the running issue during the carb balancing seems to have sorted itself out!
Maybe a seal/o-ring has reacted to a good, long soak in fuel & swollen up a bit closing off the air leak ??

Anyhoo, that's all for now folks. I'll post more updates as & when ....

Bye for now.

Wullie.

[Variablevalves suck]

Great work, good to see it out and being used.
The cbr thermostat is the way to go.

Post up your final jetting when fully fettled, will be good to get a definite setting.

[wullie3xv9]

Thanks VVS, will do .... Hoping to have a run print-out too.

[stripes1976]

Plug chopping doesn't work even on 2 strokes now with modern fuels. Only way is on dyno. If your lean at that your mains are too small I'd be looking at 120 mains and 50's to start. It will also run better with more advance which can be done by modding the pick up and side case. Your best chance is setting it up on an eddy current dyno.

[stripes1976]

I've always started at 120 mains then gone to 117.5 if needed. To risky to the engine not too

[stripes1976]

I wonder if I can pick up another 76a without the misses knowing [emoji6]

[Variablevalves suck]

Haha, you should get a 73a them 76's are all wrong.

[stripes1976]

I think my dyno graphs speak for themselves. And with the hidden gems I have hidden in the loft I reckon I could do it all again in no time. Still got some fcr's, thinwall exhaust and can. Sp1 race cdi and timing rotor. Set of 90 sp cams. And a few other bits [emoji6]

[Variablevalves suck]

I say go for it.
BUT those fcr's are so old school.