My '76 710 Goon

[datzenmike]

Couple of years ago at Canby, while poking through James's junk I found this...

 

I have a dual Hitachi SUs and intake that one day I might like to get working, and this will work the chokes. Single pull but dual cables. Unlikely to do this now as I went wirh R-1 carbs. For the R-1 carbs I only need the one cable. Inside it has an ingenious ratcheting set up with plastic gears and a track so it can't easily turn off or more on...

 

 

Looks just right under the dash. Still have not been able to start the car without spraying gas into the velocity stacks. I bought a spritzer bottle for this with a few oz. of weed eater mix in it. I also had to wire the choke on, get it running then get out, un-wire the choke and get back in. Now I can drive away and turn it off later.  I'm going to try setting the choke on while its still running and warmed up so the cylinders are over rich when I shut it down. Tomorrow I'll try getting in, set the choke and try starting it.

 

 

See the dash light dimmer above? Well the '76 comes with a small screw on mount for it under the dash. Really tacky and very 'add on'. Last weekend I got rid of it and moved it up there where there used to be an EGR warning lamp.

[datzenmike]

 

Well finally got around to some 'tuning' on these R-1 carbs. It was advised that the main jets must be increased in size from the stock 1.46-ish to 1.6mm for an L16. L18 to 1.8mm but no one could suggest a size for 2 liter engine so I went with as close to 1.8mm as I could find. Now, it runs just fine just driving around using an air fuel gauge and wide band O₂ sensor BUT floor it and let it stretch it's legs and before 3,500 it's in the 9s!!! and stays there. Last weekend I went up Mt. Washington where you can floor it and hold it for long periods. There was (I swear) a trace of what looked like black smoke behind me.

 

So I don't know how the hell a 1.8mm jet is supposed to be right, I mean it runs just fantastic but this is just throwing gas away. The R-1 swaps of 10 years ago probably didn't have a wide band for fine tuning. 

 

So I pulled four 99mm jets from old Hitachi carb primaries and bought a 0.055" drill (1.397mm) and enlarged them close to stock R-1 jets. (1.46mm) Yeah not only do Hitachi 340 primary jets fit, but that did the trick. Hits low 12s if you really try.  Originally the needle is factory set on the second notch down from the top and originally I moved them all up one notch to lower them to lean out the mid range but with the smaller jet now they were way to lean so I moved them down to the forth notch. Too rich in the mid range so up one to the #3 notch. Ding Ding Ding! Runs high 14s and low 15s level cruise but immediately drops into low 14s as you add gas and continues down as to add more. On long downhill coasting 16s and into the 17s and there is exhaust popping in the muffler.

 

I'll take out tomorrow for a real drive. Right now, I'm thrilled.

 

 

 

 

edit: Forgot to mention the incredible smoothness of the R1 carbs. The Hitachi, though in good shape, was balky and had to be driven. Where as at 1,000 RPMs in 5th you can floor it and it just picks up speed. I'm still learning how to take off  from a stop. It's practically impossible to stall where the Hitachi needs just the right amount of accelerator pump and clutch slip. Still have not tried to fix up a vacuum advance for it. It's still at 12 BTDC plus the mechanical. Right now I can't imagine it running any better. The open throats bark much louder than my quiet muffler. Not used to the noise.

[datzenmike]

Drove about 70 miles with this today. Tons of power (relatively speaking) than before. Used to have to wait for the power to begin and once revved up it starts to fall off. Now pulls all the time. I didn't think restart was that bad on the 2bbl but this is crazy fast. Docile from idle all the way up. Managed to get it down to 12.2 on the meter.

 

I also managed a cold start for the first time using the fuel enrichment. (choke) It never did that before.

[datzenmike]

Had the air horns off and noticed #3 slide would not open above half way. Ran ok like this. Took the top cover off and the spring was crooked. Set it right. Also noticed that looking down the horn you can see all the way to the intake valve.

 

I'm giving up on the zx air filter housing. I can't make it work with long or short air horns.

 

The air filter container I made rubs the hood and I'm not that pleased with it. Cost nothing but time to make it. Also I put the throttle cable in a poor spot. It's in line with the air horns and they have to be long so the cable can reach in there. I re designed the cable position and shortened the air horns 2" and this moves the air filter well away from the underside of the hood.

 

 

 

Drove into town and got some scrap aluminum plate. Going to make a much better top cover for it. Maybe I'll redo the bottom also later.

 

BTW the car started the other night with the fuel enrichment on.  Cranked for 4 seconds and boom! Had to learn not to give it any gas what ever, just wait for it to run for 30 seconds and it smooths out and the revs come up. I guess if you give it gas peddle you defeat the enrichment and it quits just like turning the choke off on a cold engine. Today it fired up on half a turn and I did this standing outside the car so I wouldn't be tempted to step on it. Gassed up, got 30 MPG.

 

Still weird to not have an idle circuit transition into a primary circuit transition into the secondary.  Slide carbs = constant velocity so mixture is more consistent and no accelerator pump or lack of, when not working.

 

 

[datzenmike]

 Cut the aluminum plate and did a better job. The other was really a 'proof of concept and it works. This one will be more precise.

 

 

 

I'm going to 'glue some fillets onto the bottom inside to position the filter better, maybe some on the top so you don't have to fiddle with it to line it up when tightening. Painted the air horns, velocity stacks, what ever.

[datzenmike]

 

This looks much neater than this...

 

 

 

[Easygoingjc]

Back when I was pulling wrenches on power equipment we had a special set of 4 vacuum gauges that we would hook to each carb and adjust each carb so all were drawing same vacuum. A smooth engine would become even smoother and throttle response increased. Tuning each carb in response to its matching cylinder.

 

Very nice on the filter housing. 

[datzenmike]

I did drill and tap the intake flanges for fittings. Did all four with the intent of later maybe working out some kind of vacuum advance/PCV/brake booster source. But haven't pursued this yet.

 

I did set each carb opening with a drill bit so they are identical. I know this isn't exactly right but...

 

The idle jets are a bitch to get at and a bigger bitch when the engine is hot. I tried 3 full turns out then 2/5 then 3.5. Idle mix is high 15s just into the 16 at 800-900 RPMs. It's smooth with the odd lean miss. However on hot restart, which is literally a 1/4 bump of the starter, it idles 18s and 19s with a few more misses. Soon as you hit the gas it drops to normal and it runs perfectly well. Do slide carbs tend towards lean when they get hot? I don't imagine they get that hot on a bike.

[datzenmike]

Raised the front end and adjusted the steering box. Much better steering response now and almost no 2" side to side play. Topped the tires to 35 PSI. Raised and checked the differential oil level... full and drippy.

[Easygoingjc]

As far as I remeber the carbs do lean out a bit once warm. The change may have been caused from heat soak. The carb body expanded where throttle plates did less. Causing more air to bypass around. Once throttle was opened fresh cool air shrunk the body and tightened everthing up again. That is just speculation on my part. 

 

May even have somthing to do with your oiled air filter changing after warm. I remeber engines would pop and fart without an air box on. 

 

I do have a tendency to overthink things. Keeps me up at night sometimes.

[datzenmike]

It's always when restarting hot. 18...19s but takes off and runs fine. I've noticed that the hot idle mix is higher than what it used to be, now high 15s 16s again runs fine but the odd lean miss. As soon as you add gas it drops and (again) runs just fine. At 50-60 cruise it's 14.7 +-. It's easy to get low 12s and maybe into the 11s. It fuckin' flies though. I can't believe how sad the 2bbl Hitachi was and didn't know it. 

 

I've ordered some jets smaller than what I drilled mine out to. 140 or 1.4mm or 0.055" or what ever number drill is closest to this. My calipers says 0.55" and change. The stock R1s that I took out are 146 so I'm smaller and still too rich top end. Remember that I started with 180s and into the low 9s!!!! I'm going to try 120/125" and if too lean move up towards where I am now.

 

It's my understanding that the main jet is for mostly above 2/3 throttle. I know it wouldn't hit the 9s till above 4K at full throttle. The needles on the slides can be adjusted for mid range and cruise to keep it in the high 14s. Idle has it's own idle mix screw but I have it over 3 turns out now. Seems like idle needs more gas. I read somewhere not to turn out more than 3 turns but not why. Could be something important to motorcycles? They are a fucker to get at and last time I took the carburetors off and flipped them in their side to see what I was doing. What I need are jets that stick out and have butterflies on the ends so you can turn them by hand in the dark.   

 

 

Heat soak. You may be right. I don't think bike carbs are subjected to heat like closed under a car hood. This weekend I'm preparing to begin working on an aluminum heat shield that will fit over the intake tubes, go down and bend out under the carbs towards the air filter. This will reflect a lot of hot exhaust manifold heat. You can run your fingers over the undersides of the carburetors but they are hot.

[Easygoingjc]

The pilot circuit is the most important especially on cv carbs. From factory epa standards caused every pilot jet to be undersized. The three turns is only relevant if the pilotjet is the right size. After  around 3 turns the taper on the adjustment screw end no longer affects metering. If you rev it up and it hangs out and rpms slowly drop it is too lean, vise versa if it drops below idle rpm and then rises back up it is too rich. This circuit ALWAYS adds fuel and is the main contributor from idle to 1/3 throttle( cruising foot). Idle circuit acts before diaphrams have time to react. So I would avise getting this dead on before adjusting needle or main jets. 

 

Also temp will affect it all. Cold air will run lean, so maybe it is hotter outside than your original tunning. 

[datzenmike]

Originally it did have a very slow return to idle between shifts requiring a change in shifting. This either went away or I got used to it. I think it got adjusted away as I opened up the idle mix but I didn't miss it. Can the pilot size be changed to larger so I have more adjustment?

 

One other thing... it back fires out the exhaust on deceleration and the air/fuel jumps up to 17-18-19s really lean. Not much if going slow but increasingly louder if gearing down or 'giving it' in a lower gear and then letting the revs fall

 

I couldn't set the idle mix other than taking them off and just counting the turns and putting back on. I know, a shitty way to do it but it's a bitch to work under them where you can't see what you're doing.... and the engine is hot.

 

 

 

[Easygoingjc]

Then I  would advice getting a jet kit with pilot jets. The bike tune was probably lean and not on a bigger engine it is worse. The decel would only be running on pilot circuit and if the jet is too small, that I would think is where the lean condition is coming from. 

[datzenmike]

46 minutes ago, Easygoingjc said:

Then I  would advice getting a jet kit with pilot jets. The bike tune was probably lean and not on a bigger engine it is worse. The decel would only be running on pilot circuit and if the jet is too small, that I would think is where the lean condition is coming from. 

 

I'm leaning this way also. Regular carbs are similar on deceleration. 

 

I have generic jets coming and will size them as I try them. Start small and go up. 

 

Any idea how the idle adjustment (pilot?) jets are gotten at? I haven't explored these carbs much. Pretty much all I've done is remove the bottoms of the float chamber to get at the mains.

[Easygoingjc]

There should be a smaller jet under the float bowl also closer to the engine side of the carb. May take a small flat screwdriver down the pickup to get to it. If I remember correcly.

 

 

[datzenmike]

Yes, that's where they are, I've adjusted then but not when running, which I should. A prick to get at. 

[datzenmike]

Well last weekend went for a 200 mile joy ride with lots of twisty turns. Car ran very well. Brakes worked... was climbing up hill in the right of two lanes with a single coming down. Was no more than 55 MPH and preparing to merge to the left as this lane ends and some idiot pulls up to the stop sign from a side road and rolls through it and stops in my lane!!!. My luck if I pull over to the left they will gun it to get out of the way and I'll T bone them. I'm slowing but had to lock up the brakes while they decide that they should back up. As they begin backing up I can see that I can go around then on the left if I have to, so no worries. They get out of the way and I get stopped right where they were stopped. They both seem surprised so I look at them and shake my head and drive off.

 

The insurance ran out Thursday so time to get to work. Got an aluminum serving tray for $3 and made a heat shield out of it.

 

 

Will finish hooking the carbs to the intake and it will hide the art on it. Probably will run the fuel line directly through a hole just above #2 and #3 ports where I had it originally.

[datzenmike]

[Easygoingjc]

Looks good.  That should keep away most of that radiant heat. 

[datzenmike]

Don't know if heat is a problem but hot restarts are different from sitting hot restarts if you know what I mean. Idle goes very lean 18 19 20s but immediately goes away if driven or given the gas. So it would seem it affects idle only. I did have the coolant flowing through the carbs but this was last spring and, at that time, didn't notice any difference so disconnected it. 

[Easygoingjc]

The only benefit I could see for having the coolant flow through the carbs would be for a cold weather carb tune. Because there is no temp compensation and you have a tune for warm weather, it potentially could run lean if you decided to take a trip on a cool day. Once warmed up on choke circuit, the coolant could warm the body and incoming air a little and richen the mixture. You would some how have to stop flow during the warm weather to keep this effective I would think.

[datzenmike]

I guess the bike application is on all the time. On the L series head, coolant flows all the time through the intake and in extreme heat actually 'cools' the intake, removing radiated heat from the too close exhaust manifold.

 

I disconnected and plugged the pipes because it was a PITA to remove every time the carbs were off. Haven't really explored this yet. Unlikely to drive this in cold weather. 

 

Can't see bike carbs being exposed to a lot of heat, but?? 

 

 

Slide carbs take getting used to. You can't pump the gas when starting, (there is no auto choke and no accelerator pump for enrichment) just set the hand 'choke' and crank. The enrichment circuit is pretty much defeated if you step on the gas during start, and engine will stall unless given 30 seconds to warm? There are no flat spots off idle, no lag or falling on it's face if you stuff the throttle in too high a gear at too low a speed. Fuel and air are near perfect and it pulls away smoothly, no hick-ups or balks. No transition from idle to primary to secondary. There's no pumping the gas to rev the engine just before clutch engagement. I find the revs come up so smooth/quickly that I tend to give it too much gas on take offs. You can literally pull away on idle throttle and step into it. While not impossible to stall on starts, it's very strong and resists stalling. It's damn hard to loose 50 years of carburetor driving away from a stop. 

 

Still don't have a working vacuum advance. It runs so well, so improved I haven't even thought about it.

[datzenmike]

 

 

These were $12 CDN for 20. I got all under 120 so I can drill them to any size above this. AS mentioned previously it was recommended 180 for a L18 on the 'R-1 lots of pictures' post but my air/fuel gauge dropped to 9.4, I think that's the lowest reading there is, so it may be lower. This was 10 years ago and no air/fuel readings were supplied. It runs great below 10 but would run just as great in low 13s and use less gas. This is at WOT above 4K. I re-drilled 4 Hitachi 99 carb jets to 140, very close to what the R-1s came with and this raised it into the 11s. Running out of jets so I got these from Amazon for tuning a single cylinder bike carb. They range from 95? to 115??-ish.

 

Going to get a 120 or 1.2mm drill or the inch equivalent.  The 140 was 0.055", 120 should be 0.04728". By going small I can always drill larger and sneak up on the correct ratio. I would like to just barely hit into the high 12s when really giving it.  The drills are about $8.

[datzenmike]

Need a 1.2mm or 0.04721" drill, got a #53 drill which is 0.465" so good enough. Only thing closer would be a 3/64 which is 0.0469" but there wasn't one. 

Prepared 4 new jets to just under 120 size.

 

To recap the R-1 came with 146 (1.46mm) jets. Popular wisdom says to go at least 180 so I drilled them out but air fuel at WOT drops to mid 9s and maybe the gauge doesn't read any lower. I drilled some jets to 140 and now in the 11s. Bought a bag of tuning jets and drilled out to  1.81mm or just under 120. Weather willing I'll slip these in tomorrow and see if I can get WOT up into the high 12s.