Another carburetor rebuild ....

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Steve72J
Posts: 28
Joined: Fri May 18, 2018 1:25 pm

Another carburetor rebuild ....

Post by Steve72J »

Back on the road again with the old 72 GT750. Found 2 out of 3 inlet nozzles gummed up in the old Mikuni 32mm carbs. The jet needles looked like they had been smeared with shellac. The float needles were remarkably clean somehow. All the orifice holes were plugged on all 3 pilot jets.

Back in February I found the petcock completely filled with trash and had the tank acid washed and lined. Dipped the carbs and the Berryman carb cleaner ate though the Mikuni finish and left a terrible chalky grey residue that was removed only by boiling them in water and Pine-Sol, and even then wiping the carb with your finger would reveal a light grey smear on your finger. Wipe, wipe, wipe forever and then put them back together. Added the stabilizer and all was good for three months

The only change in ten years of riding this bike was the recent additive of STA-BIL Fuel stabilizer. Have always use the same Chevron station down the road. Bike hadn't been ridden much since I rebuilt the carbs back in February and but ran great when I did, for about 3 months. I asked the station owners if they'd had ever had any complaints and they said "no". This time, even being very careful, one bowl shattered getting it off (had a crack previously repaired with JB Weld), and a slightly corroded float pin retainer broke. Rummaged around in my old parts bin and found replacements. So is it the additive , or the old dissolved finish lingering in hard to clean passages, or possibly just bad gas ? Can't do this every two-three months.

Found a supplier of ethanol-free gas a few miles away and going to try some ...but damn, that stuffs expensive.

PS: Found a solution of Wintergreen Oil and alcohol made the carb rubbers like new. It was really amazing ...the video says a week soak, mine where soft after an overnight soak.

https://www.youtube.com/watch?v=C5SQ_vJmt64


A mechanic buddy says he'd never use Sta-Bil fuel stabilizer, had some bad experiences with marine engines using it.
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PaulD738
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Joined: Thu Sep 25, 2014 6:57 pm
Location: Warrington Cheshire

Re: Another carburetor rebuild ....

Post by PaulD738 »

Depending on where you live Esso super unleaded is ethanol free. I stripped and cleaned the carbs, fuel tap and tank on my 750J when I got it over three years ago and I never had any problems using Esso’s finest. See pics for proof of what ethanol can do to our fuel systems.
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They're rubbish them Jap bikes lad they won't last five minutes! you want to get yourself a nice Royal Enfield!
A quote from my old dad 8-)

I started out with nothing and I’ve got most of it left!
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BAZ
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Re: Another carburetor rebuild ....

Post by BAZ »

Did the bike come from the USA that looks like unleaded fuel left in the chamber, I think people are maybe making to much of the problems with modern fuel..
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PaulD738
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Location: Warrington Cheshire

Re: Another carburetor rebuild ....

Post by PaulD738 »

BAZ wrote:Did the bike come from the USA that looks like unleaded fuel left in the chamber, I think people are maybe making to much of the problems with modern fuel..
Yes Baz my 72 J was from the states and as you can see was in a bit of a state :lol:
The thing is America has been using ethanol in their fuel for a long time so most bikes imported from there are in a right old mess. The plastic & rubber bits came from my fuel tap!
They're rubbish them Jap bikes lad they won't last five minutes! you want to get yourself a nice Royal Enfield!
A quote from my old dad 8-)

I started out with nothing and I’ve got most of it left!
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Chris57
Posts: 147
Joined: Wed Mar 16, 2016 8:04 am

Re: Another carburetor rebuild ....

Post by Chris57 »

PaulD738 wrote:
BAZ wrote:Did the bike come from the USA that looks like unleaded fuel left in the chamber, I think people are maybe making to much of the problems with modern fuel..
Yes Baz my 72 J was from the states and as you can see was in a bit of a state :lol:
The thing is America has been using ethanol in their fuel for a long time so most bikes imported from there are in a right old mess. The plastic & rubber bits came from my fuel tap!
2 mates of mine in the US started finding issues with classic car & bike fuel systems way before we did due to ethanol being added, some of theirs has 15% of the ba5tard stuff in it now :(
Steve72J
Posts: 28
Joined: Fri May 18, 2018 1:25 pm

Re: Another carburetor rebuild ....

Post by Steve72J »

Went to a local oil/gas distributor and bought 2.5 gal (9.5L) of 93 ethanol free gas/petrol. Their meter showed 3 gal but they begrudgingly me charged for 2.5 gals. since that was my cans capacity. Won't be taking the bike there for fill ups, just the can. Al least I'll have a leg to stand on when when they try to overcharge me again @ $4.50 per gal . (1.86GBP)

Took the GT for a test spin and the difference is amazing. Short ride to test the timing and carbs, found another hairline crack in the left bowl .^*^%$$#@. Buffed it, installed the bowl again and used a paintbrush to apply some JB weld.

Not a single bowl showing up in Ebay or Google searches. Couple of rough looking carbs for a ridiculous amount of money ($169). One carb body and bowl (no top or slide) for $69 but looks like crap and selling without inspecting it.

Parts are getting extremely scarce and pricey over here since I first got this bike in "2004". Back then almost every part could be found with with in various stages of condition. I'd got lucky and found a parts bike for $100 back then and anything usable from it now fits in a couple of small bins.

Hope to make the 50th Anniversary in 2022, looking grim.
teazer
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Re: Another carburetor rebuild ....

Post by teazer »

I'm pretty sure I still have a set or more of 72 carbs if you need them for less than 169 bucks a pop. Where are you located?
Steve72J
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Joined: Fri May 18, 2018 1:25 pm

Re: Another carburetor rebuild ....more drama

Post by Steve72J »

.. leaked fixed at the bowl bottom. Looks like is was cracked from lack of clearance of the top clutch cover screw flange. JB' welded.

Then found another crack in the 6 mm drain hole. But this parts bike had been sitting in dirt for years, Rims were rusted to the hubs and the bike was buried down to the chassis. We had to rock it back and forth to free it. Still a steal for all the good parts I salvaged of of it.

Used a mini torch and filled 6 mm drain plug holes with solder. Not the bowl hole, but the drain bolt that's drilled for just loosening and without removing. So far so good.

Hope to get it inspected this afternoon. Not current since 11-17
Steve72J
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Joined: Fri May 18, 2018 1:25 pm

Re: Another carburetor rebuild ....finally

Post by Steve72J »

Failed inspection due to flickering headlights. Went back home and pulled the switch apart, cleaned it, in the process of ...a wire became "unsoldered" ...repaired that and went back to the inspection station. They didn't even check it, just handed out a sticker. Been going there for years, got to bullsh^% with the guys and forgot to pay them. Went back, gave them the $7 and then went to the tax office and renewed my plates.

Got a "Motion Pro Cable Luber" coming from Amazon next week and after lubing the cables I'll adjust the brakes, detail the bike, and call this project DONE. Once again thoughts of selling the bike have vanished, just so much fun to ride
Steve72J
Posts: 28
Joined: Fri May 18, 2018 1:25 pm

Jackpot ...

Post by Steve72J »

After "JB Welding crack after crack, bottom of the bowl repair was successful, then a crack by the left rear mounting hole showed up, then the drain hole literally disintegrated. Thought I had it solved until the mounting hole started seeping gas again.

After a futile searching Google for 3 days I ran into a guy at a convenient store who said to try Houston Motorcycle salvage in Pasadena. Been there once about 10 years ago and had forgotten all about them.

Took the 16 mile trip today and found a milk crate full of bowls. Pull one perfect bowl 1972 and another good bowl (with the exterior nozzle on the overflow). Also a 1972 310 12R carburetor complete but for the slide choke plunger. Took all three items for less than half what a "Not inspected " single "72" "32 mm carburetor" from Ebay that looked like it was dug up from somebodies back yard.

Had a great chat with the owner too ....http://houstonmotorcyclesalvage.net/
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