jltucker81 Posted June 28, 2019 Report Share Posted June 28, 2019 Does anyone have experience with a 1981 720? It has a brand new, stock carburetor, other day throttle stuck wide open on freeway, i thought it was the cable, i was wrong. I've messed with everything i can, I've done research, i'm hoping this is something common and simple, any input would be much appreciated... 1 Quote Link to comment
datzenmike Posted June 29, 2019 Report Share Posted June 29, 2019 Hard to find a real new stock carburetor these days. They would be around $860 at the Nissan dealer. What you have is probably a 're-conditioned' carburetor which has been rebuilt with who knows what quality parts and labor. I guess you managed to get it to close and got home? With the engine off floor it from inside the cab. Can you get it to jam again??? If cable not adjusted right you may over extend and bend things. Does it catch on anything? Is the carpet in the way? Watch the linkage with the air filter out of the way. Anything binding? I've had an accelerator pump piston jam in the cylinder and not return. 1 Quote Link to comment
jltucker81 Posted June 29, 2019 Author Report Share Posted June 29, 2019 The carb came from ebay, Maybe from china or something. We towed it home, I've got the air cleaner off and the cable completely slack, still winds straight out when started, I've been through the haynes manual, no luck there, the next thing i plan to do is go through replacing vaccum lines. How can i check the accelerator pump? Would that cause it to stay tached out? 1 Quote Link to comment
datzenmike Posted June 29, 2019 Report Share Posted June 29, 2019 Take the air filter top off and look down the secondary barrel with a flash light. It's the one closest the valve cover. Should be closed. Maybe something stuck in it. 1 Quote Link to comment
jltucker81 Posted June 29, 2019 Author Report Share Posted June 29, 2019 I'll take a look, thanks. 1 Quote Link to comment
bottomwatcher Posted June 29, 2019 Report Share Posted June 29, 2019 New carb but may have been sitting on the shelf for a while. Lube dries out and becomes anti lube "sticky". Use WD 40 to loosen things up. Soak anything that moves and move it. Once things are free and moving time to use an actual spray lube "WD 40 evaporates". I use corrosion block or boeshield but it is extremely expensive so someone on here may be able to recommend something cheaper. Good luck and the stuck throttle can be scary. 2 Quote Link to comment
jltucker81 Posted June 29, 2019 Author Report Share Posted June 29, 2019 The larger butterfly, closest to the valve cover is closed, the one on the other side, under the choke is open about quarter of an inch, could it have something to do with the fast idle cam? How do i post pictures? Something about a url 1 Quote Link to comment
jltucker81 Posted June 29, 2019 Author Report Share Posted June 29, 2019 This thing has been running fine for months, had it smogged a few weeks ago, technician was impressed with how it ran... First time on freeway with it and bam. 1 Quote Link to comment
bottomwatcher Posted June 29, 2019 Report Share Posted June 29, 2019 This is a simple mechanical issue. Don't run the engine just look down the carb throat and operate the carb by hand. Something is hanging up. 1 Quote Link to comment
datzenmike Posted June 29, 2019 Report Share Posted June 29, 2019 Quarter inch is way too much for the fast idle. Also not really 'stuck wide open'. Agree it's mechanical. Look at it while opening the throttle by hand and watching it close to a stop. 1 Quote Link to comment
jltucker81 Posted June 29, 2019 Author Report Share Posted June 29, 2019 That's what I'm thinking too, but nothing i do frees it up.. I'm gonna take the carb off so i can really check it out, i just got twelve feet of vacuum line, gonna go through them in the morning before i remove the carb.. Thanks for the input guys, much appreciated.. 1 Quote Link to comment
datzenmike Posted June 29, 2019 Report Share Posted June 29, 2019 It won't be a vacuum line. Can you still open the throttle further or is it seized? 1 Quote Link to comment
jltucker81 Posted June 29, 2019 Author Report Share Posted June 29, 2019 Not seized, just won't completely release... 1 Quote Link to comment
jltucker81 Posted July 3, 2019 Author Report Share Posted July 3, 2019 Well i found the problem and I'm just confused, i don't get it... The adjustment screw for the fast idle cam was completely tightened, if it were to be tightened any more it would fall out the other side... How is it possible that it ran fine for months and all of a sudden this happens.. Makes no sense at all, couldn't have vibrated tighter, it's difficult to turn... Wtf? Some kind of magic involved...bahahahaha 1 Quote Link to comment
datzenmike Posted July 3, 2019 Report Share Posted July 3, 2019 The fast idle screw should have a nut on it to hold the setting. 1 Quote Link to comment
jltucker81 Posted July 3, 2019 Author Report Share Posted July 3, 2019 Thanks man.. Do the reed valves on these wear out? I'm sure this one is from 1981... 1 Quote Link to comment
jltucker81 Posted July 6, 2019 Author Report Share Posted July 6, 2019 What would cause this thing to ping when pull a hill after it's good and warm? Is there a way to tip you for the help? 1 Quote Link to comment
bottomwatcher Posted July 6, 2019 Report Share Posted July 6, 2019 Over advanced timing. If pinging related the timing until it goes away. Throw up a new post when you have a new problem 1 Quote Link to comment
datzenmike Posted July 6, 2019 Report Share Posted July 6, 2019 1/ Would be the ignition timing set too advanced. Should be 12 BTDC on an L20B. Try 11 but not much less than this. It should run at 12 so look for another cause first. 2/ Wrong spark plug with wrong heat range. Use only NGK plugs..BP6ES11 should be the same as the '78, but if you find another number from an '80 FSM definitely go with it. 3/ Engine is slightly over heated. Gauge should be at or a hair above the halfway point in the 'run range'. 4/ Poor octane gas. If the timing and temperature are right it should run well on the cheap stuff. Try a different brand than your usual. 5/ Combustion chambers sooted up with carbon from running with the choke on too much or choke not shutting off fully. Could be the carburetor is flooding causing an over rich mix. Take for a drive and let er go a bit. Engines are self cleaning if given the chance. If you want to tip I'm sure Jeff (Icehouse on Ratsun) wouldn't turn down a donation to Ratsun... https://ratsun.net/profile/3-icehouse/ Contact him by Private Message and set something up 1 Quote Link to comment
bottomwatcher Posted July 6, 2019 Report Share Posted July 6, 2019 Retard frigging autospell! 1 Quote Link to comment
jltucker81 Posted July 6, 2019 Author Report Share Posted July 6, 2019 thanks guys, you're a big help for sure.. Do i need too have mt own website to post a pic? 1 Quote Link to comment
jltucker81 Posted July 6, 2019 Author Report Share Posted July 6, 2019 My little truck's looking pretty badass... Just want to share... 1 Quote Link to comment
datzenmike Posted July 6, 2019 Report Share Posted July 6, 2019 No. Join a picture hosting site like imgur (free but you can pay for extras) or there are many others but I do not recommend photobucket. Take your picture there for storage. When you want to post it here, go there and copy the picture information and bring it here and paste it. This is very abbreviated. 2 Quote Link to comment
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