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Just bought a 521


mainer311

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Guys, I’m having a new problem that seems easy to solve, yet I’m a bit stumped.

 

The truck runs fine for a while when cold, but as it gets up to operating temperature on these hotter summer days, my throttle is “sticking,” and behaving oddly. I put sticking in quotes because that is what it seems like, but the throttle isn’t actually stuck. Between shifts, with the clutch in and my foot off the gas, the RPM’s hang at whatever they were prior to me pushing the clutch in. It makes shifting a bit annoying, since the clutch slips a bit and then the truck lurches on the upshifts. If I blip the throttle, the RPM’s will then come down to a normal idle.

 

My initial thought was a sticky throttle cable, but upon playing around with the carb, it’s not stuck at all. I even left a little bit of slack at the idle position to account for sleeve expansion with the hot engine bay. The throttle cam always comes back to resting position on the idle adjust screw.

 

What would cause the RPM’s to hang until I blip the throttle? My other guess is that the secondary is staying stuck open, but I haven’t investigated that yet.

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Is this an L20B? maybe an L18? It may have a BCDD which slows the rate at which the idle speed returns to 'normal' if it's out of adjustment it won't 'reset' properly.

Hi2-DCH340.jpg

 

It's the roundish thing with the 5 screws holding it on. Pop the rubber cover of the adjusting screw in the middle and turn counter clockwise to reduce the sensitivity.

 

Could be the secondary. Next time shut off while it's high revving, maybe use the clutch to help stall it. Then look down the secondary with a flashlight.

 

Could be the throttle shaft on the primary is worn an oval hole into the casting of the primary. The throttle plate rubs and sticks to the side of the barrel. Again shut off when it's doing this and watch to see if it will click shut when moved.

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It’s just the stock L16 with the stock hitachi. I rebuilt the carb this past winter and didn’t notice anything, but that’s not to say something went amiss between now and then.

 

Mine has the anti-dieseling solenoid in that location, which doesn’t work anyway. The truck runs the same whether the solenoid is plugged in or not. I’m not really sure how that’s possible, since the solenoid is spring loaded and “opens” when power is applied. 

 

I’ll see if I can get it to create the problem in my driveway and then shut it down to investigate.

Edited by mainer311
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I wouldn't waste anytime on it, just get a weber and throw that Hitachi away.  

 

Also sometimes mine hangs but not at the RPM I left it at.  IE 90% it hangs around 700-750RPMs but sometimes it will stick at 1000.  Usually just stab the the throttle to get it back down.  I think Hainz has the same problem but why it does it idk. 

Edited by d.p
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Yeah, mine does that too. And when it gets bad, it hangs anywhere from 1500-2000. I just looked at it (cold) and can’t find anything wrong.

 

Also just installed some headlight visors. I really like the look.

 

GI2dunR.jpg

Edited by mainer311
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Update on the carb:

 

I let it sit idling in the driveway for a while while I weed whacked my lawn. Came back and revved it up to 2500 for a few seconds and lightly let off. Idle only came back down to 1250 or so. I pushed on the throttle cam and sure enough it immediately fell to about 750. I put a slightly stronger return spring on it, so I’ll see if that makes any difference while driving.

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The accel pump has a stiff spring, but sloppy linkage. This is a 328 Hitachi, so it doesn’t have an extension spring like the late ones, it’s a torsion spring on the pivot.

 

Either way, I can push the cable cam further closed. The stronger spring made the symptom go away.

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  • 4 weeks later...

Tonight I decided to finally do something about my broken hood prop. The previous owner gave it to me in pieces when I bought the truck. He had been using this ugly yellow stick to prop the hood up, and every time I’d work on the truck, I’d bump it and the hood would close on my head.

 

I took a small piece of 3/8” (beefy!) low carbon steel rod and tapped one end for a 10-32 socket head screw. I then heat the rod up and bent it to fit the lower mount. I then used the old rod for an approximate length template. The old rod has two right angle bends very close together at the end, so I couldn’t quite do the same with mine. I then trimmed off whatever I didn’t need from the end. I installed the hood prop, and then secured the tapped end with a couple washers and a SHCS.

 

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Thanks. I love tinkering with it, but unfortunately right now, there’s not much to tinker with. 

 

For that reason, I’ve been working on my 620 model kit that my parents found. It’s by far and away the worst fitting, shitty model kit I’ve ever experienced. Nothing I can’t fix though.

 

19LYxCd.jpg

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Decided on candy red for the valve cover, trying to replicate the RB26 look. I was torn between that, or red wrinkle, or black wrinkle. It’s not quite done yet. The letters will carefully be sanded off back to aluminum. The oil cap is from Williams Machine.

 

I wiped the engine bay down and organized a lot of the wiring. I’ve been trying to get it ready for Japanese Car day in October.

 

vLtL079.jpg[/img]

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So, I stumbled on something strange with my truck. I noticed that the anti-dieseling solenoid disconnected itself at the bullet connector, yet my truck still idles and drives fine. I thought that was strange, so I removed the solenoid and tested it on the battery...yup, it works! So I tested the leads going to the solenoid from the harness, but I get no voltage when the ignition is on. Odd. The spring and plunger are still in tact, so if the solenoid isn’t getting activated at all, how does my truck continue to idle fine?

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Pretty happy with the engine bay now. Relocated my headlights relays to the passenger inner fender, wire-loomed some stuff, installed the valve cover, wiped the whole thing down, bundled and zipped-tied some stuff, and to finish it off, I turned the heads on some stainless socket heads, polished them and installed on the valve cover with some copper anti-seize.

 

0TrnWn0.jpg

 

blkctoh.jpg

Edited by mainer311
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3 hours ago, mainer311 said:

So, I stumbled on something strange with my truck. I noticed that the anti-dieseling solenoid disconnected itself at the bullet connector, yet my truck still idles and drives fine. I thought that was strange, so I removed the solenoid and tested it on the battery...yup, it works! So I tested the leads going to the solenoid from the harness, but I get no voltage when the ignition is on. Odd. The spring and plunger are still in tact, so if the solenoid isn’t getting activated at all, how does my truck continue to idle fine?

 

If the idle is too high the idle cut has no effect.

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1 hour ago, datzenmike said:

 

If the idle is too high the idle cut has no effect.

 

My idle is like 650rpm. Truck idles great, actually. If I push the choke in too soon, it’ll idle around 500, but it starts getting grumpy.

 

Edited by mainer311
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