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Build Thread: 74 GT-750

gear position indicator, no?

You may be right about that, but that's not what I was thinking. The GT750 was the first mass produced bike that I know of to have dual front disc brakes. Honda had come out with the single on the CB750, and others introduced singles, but AFAIK Suzuki was the first mass produced bike to have dual front discs.
 
You may be right about that, but that's not what I was thinking. The GT750 was the first mass produced bike that I know of to have dual front disc brakes. Honda had come out with the single on the CB750, and others introduced singles, but AFAIK Suzuki was the first mass produced bike to have dual front discs.

huh. had a ... 72? H2 with dual fronts, but it was an option as I understood it, now much sought after. can't believe I sold it for $1,800 in the late 90's...
 
huh. had a ... 72? H2 with dual fronts, but it was an option as I understood it, now much sought after. can't believe I sold it for $1,800 in the late 90's...

My 72 had a drum up front. The dual discs became standard in 73, IIRC.
 
The carbs back together and ready to press back into the boots tomorrow. A few issues were addressed: the needles were on 4th clip vs recommended 3rd. Mains were 110 all around vs 110 R & L, 107.5 Center. Pilots were correct at 47.5. Pilot air screws out 1/2 turn vs 1/4. Floats were all high for low fuel levels, but that "tilt 10-30* and measure float height" always seems off in real life for me so I usually find that I have to lower the fuel level after the initial recommended adjustment.

Just overall filth. Going to attempt to fire it up for the first time in the morning off the motionpro fuel bottle, fingers crossed.
 
Carbs are cleaned up and back in - lord those intakes are a tight fit, some veins up in the neck pushing the carbs back into the boots - and air filter pods are on, fuel in the bottle. Given the state of the petcock I'd think that I've got petrol that has gone past the float valves and into the crankcase. So I'm not wanting to fire it up with an unknown transmission oil state, so might as well get all the oil I can out.

So a bunch of questions for this morning:

1) If one wanted to get ALL the transmission oil out then I'd remove both the oil drain bolt and the angled trans shift drum detent bolt? Manual says that 300cc or so is left behind if you don't split the cases (note on pg 42) so I'm thinking that pulling the detent will drain that remaining 300cc out

IMG_1023_zpstgvrqai2.jpg


2) Replace both bolts (without moving the bike at all to get the shift drum detent back in correctly) and fill to weep hole which should be 2500cc - normal 2200 + 300cc from shift detent draining, correct? Do I trust the weep hole, or do I measure the new oil and ignore any weep overfill or underfill condition?

3) I run Mobil1 5/30 in all my other bikes, any issues with running modern synthetics? Manual calls for 20/40 which is an odd grade

4) I don't see a torque value for the 2 drain bolts in the manual, so I'm assuming the German torque value of GutenTight

5) And finally, how does one confirm visually that the oil pump is actually pumping oil into the cylinders? The bottle has gas mixed at 30:1 out of the dirt bikes just to be sure, but I'd like to feel comfy that the oil pump is doing its job
 
Tried to fire the bike up last night. Some fuel weeping slowly from the non-OEM float bowl nut (13247-31210, $3.50, discontinued, $13 on fleabay, crap, don't want to spend money on these carbs...)

As expected there was fuel in the oil. Drained the case well - but what a mess it made underneath, some of the wiring runs right next to the plug so of course the oil followed the path of least resistance. Cardboard caught all of it. Will address all that when the motor gets pulled for cleaning/polishing and wiring updates. Then measured out 2200cc in my ratio-rite mix cup and poured it in but nothing out the weep hole while bike is on the center stand. hmmm.... Added another 200cc, still nothing out the weep hole. Figured I had more then enough new 30wt in there so I buttoned it up.

Then found that the battery was pretty knackered after a few attempts. So off to grab a new one last night and filled it with acid, decided to let it sit overnight to let the levels stabilize when the garage temps hit 30*f/-1C - seemed like a good time to come back in the house and call it a night at that point. Currently about the same temps outside this morning, need another hour or 2 before getting back to install the new battery and have another go at getting it fired up.
 
5) And finally, how does one confirm visually that the oil pump is actually pumping oil into the cylinders? The bottle has gas mixed at 30:1 out of the dirt bikes just to be sure, but I'd like to feel comfy that the oil pump is doing its job

Great bike :thumbup I have always wanted one of those after having been loaned one in my youth for about 3 months.

Regarding your #5 above, if you go to about 1 minute in this video you will see what I did to ensure the oil pump was working on the RZ500. The clear lines are cheap temporary stuff from OSH. Watch a little longer and you will see the oil pumping thru the clear lines.

https://www.youtube.com/watch?v=uzOyGdQiBn8&feature=youtu.be


I found it quite interesting how much (or little) oil is fed to the engine from the oil pump. Could be quite different volume on your beast but same theory of course.

Good luck.
 
[youtube]bPmVhyHBRAM&t=0005[/youtube]

Finally got it fired up. It didn't run great, but this should help explain why

IMG_1024_zps2demo4lz.jpg


Puking fluid from the middle cylinder. Thankfully I'd left the cardboard from last nights oil change on the floor to catch any lingering drips. Going to put an old dish tub that I use for cleaning underneath the middle pipe split connection to catch as much as I can along with more cardboard to get it cleaned all the way out.

Went out and grabbed some new 5/16-8mm clear fuel line. I was trying to make some old kart fuel line work, and it cracked in the cold at the carb fuel inlet point. One of the float bowl connector lines is weeping too so I guess I'm resigned to pulling the carbs again and going back through them. Meh

More to come
 
So went back out and fired it up. L cylinder not firing, pipe is cold and as it warmed up the bike started to run worse, bogging. Not crisp on the throttle at all. Killed it and pulled the plug and grounded it and hit the starter. No spark. Pulled the coil pack out, going to clean it all up. Some green corrosion on the plug wire off the L coil where the plug cap screws in. Will cut the plug wire back a bit and reinstall the cap after checking the ohms on it. Tomorrow

Happy New Year to all
 
Finally got it running on all 3 cylinders, and have heat in all 3 pipes. Had to do some plug juggling that, for some reason, solved the L cylinder not firing even though it had spark. :shrug:

The L cylinder white wire off the points to the coil was the problem. It's a horseshoe style connector (just like the one on the condenser) and one of the legs was missing and it wasn't attached well to the points so there was no connection, so nothing happened when the points opened. As I was tracing the wires between the points and the coils it took me more than a few seconds of staring at the wires in the area under the L side cover to figure out that the 3 wires coming off the points to the connector there had no male connector body - the spades were just plugged into the female plug "... wth, this just doesn't look right.... <pause> oooooohhhh, huh <note to self that this will get cleaned up with the rewiring>"

Carbs are still lean on the idle circuit at 1/4 turn so it bogs out and dies after a few moments off the choke. Idles cleanly for a minute or 2 till it leans out and dies off. Carb tuning day tomorrow.

Did a compression check - L: 100, C: 115, R:105

Baby steps, baby steps
 
While I've been quiet for a few days there has been a bunch of progress.

Now that the GT is proven to run I've moved the R1 down off the bench and moved the GT up. The stock pipes are off getting ready to be sold off to help offset the cost of new Jemco's. Pulled off footpegs, shift arm, and the swingarm.

Have had a roller 92 GSXR750 in the way in the garage for 3 years that I'm finally getting to use as a donor for the GT. Got the swingarm pulled out of the roller, and have it installed into the GT, needed 2mm cut down off of each pivot boss face - dirty work. Going to reuse the skinny GT pivot bolt and going to machine the fatter GSXR pivot bolt as the adapter sleeve, brilliant idea I thought.

Need to get the sprocket face cut down on the donor carrier quite a bit to get the chain to clear the frame. The sprocket on the carrier right now is somewhat offset so that will help. Once I figure out how much offset I have with the carrier face cut down I'll need to find a source for offset front sprockets. Planning on running the 3 spoke alloy wheels for the time being to get the suspension shaken out, then look into the spoke setup in phase 2.

Front end is coming off later today, need to see how close the 92 steering stem is to fitting and either have it adapted or have the GT stem pressed into the 92 triple. Ernie my machinist is going to be busy.

Tank is finished with its electrolysis bath. Used regular baking soda instead of the washing soda, seemed to work ok. If not I can run it through again. Coated the inside with about 200cc of 2 stroke oil that is sitting in there now that I roll around in the tank when I walk by it now and again. Came out ... ok. The fuel filters will tell the final story once it's on the road after running a few tanks of gas through it.

Built a list of socket head bolt sizes that I'll need for the engine cases to try to order in A2 stainless through the local Fastenal store.

Currently thinking that the paint is going to be Lexus Jade Green. Had the color on a 92 SC400 and loved it, hoping it will work well on a bike, we'll see. Everybody does that blue which looks great, but I'm looking for something different.

Put an email message into Autocar about sources for a Newtronic ignition, we'll see if I get a response. Found the guys at http://www.motorcycle-ignition.com.au/motorcycle_ei_kit.htm who sell the Newtronic, they've got the ignition kit for $296 AUD (212 USD) + $28.25. Any other places to purchase at? I see Marcel at classicsuzukiparts.nl has a unit for $199 plus €19 shipping as well

Hoping to get the Jemco pipes and electronic ignition ordered this week.
 
I just found this post,
If you don't get any answer on the Newtronics from AU, that's normal.
I gave up and worked with Yambits in the UK.
They may be able to source a Suzuki kit but with the volume of kits they buy and sell, they have the clout with the Newtronics distributor(s) so THEY will get an answer.
They have very fair pricing too.
 
no answer from anybody re: newtronics. While I like the granularity of having individual cylinder timing control with the newtronics, if I can't find anybody interested in selling it to me then I'll def have trouble finding someone to support it later on if I have trouble. Pretty pricey too. But I went ahead and ordered the Accent EL3ZCoil unit from Uwe at accent-electronics.com in Germany, ran me under $190 shipped, nice looking unit.

ignitionSet.jpg


Got the Jemco's ordered today as well, they should be here by mid month.

Steering head bearings from All Balls to graft the GSXR front on arrive tomorrow so the front should be installed by the weekend. I realized I neglected to measure the original geometry, so I need to put the forks and swingarm back on and get the tape and pen/paper out first. Vague sense that the 750 forks are going to be too short, I have an eye peeled for 1100 forks from the same year/series that should add 30mm or so to the fork length

Anybody have a clapped out 170/60-17 rear tire that they want to get rid of? The rear rim is without tire (I cut the tire off a few years back to make the roller easier to store) and I need one to get the sprocket carrier spacing offset and ride height set. The tire will just need to hold air, it'll never see the road, for mock up only

It's really howling up here tonight, rain going sideways, and lots of it, big winds. Strong magic afoot.
 
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The thing about the Newtronics,
you won't have a problem down the road.
I've had one in my old Yam triple for 8-9 years?
still perfect .
You should drop by a bike shop and just get a take off tire.
we have some 170's here, but the shipping would be silly to pay.
although, I know a guy who lives in Fresno and Sonora both who would take it to you.
he's in town this week too. I'll email him.
 
I might have the old 170 /60 tire from my vfr. let me check tomorrow.
 
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