Author	[Modern View]
Hiker_64 08-12-2012 05:17:02 166.147.121.146 Report to Moderator	New 8n owner and new to the site, look forward to learning from everyone. According to FO-4 the idle and main jet should be roughly one turn out. Yesterday I bottomed both and the main jet was 4 1/2 turns while the idle was 2 1/2 out. The motor runs okay with an occasional stumble and is idling at about 700 rpm with the quadrant all the way back. Plugs and points look fair with no fouling. Question is would this carb benefit from a rebuild and if so, the basic or comprehensive? [Reply]   [No Email]
Hiker_64 08-12-2012 12:56:29 166.147.121.146 Report to Moderator	Re: 8n carb in reply to Hiker_64, 08-12-2012 05:17:02   Thanks for all the quick and detailed responses? Went to TSC and picked up the full rebuild kit, already had a gallon can of carb cleaner from doing the chipper this spring. Everything is now back together but as soon as I hit the start Murphy struck and my battery is dead. The only charger I have is a 2 amp battery tender so its going to be a while. The carb was extremely dirty and funky and it seems some one had buggered the heads of the jets. So those are replaced. Only had to grind one screwdriver for the economizer jet. I will follow everyone's advice and report back after the battery is charged. I bought the old girl to maintain my 2000' driveway and some light gardening, but I have found I enjoy wrenching on her as much as do using it. I'm going to have plenty of questions moving forward and am pleased to have found such a friendly and helpful bunch [Reply]  [No Email]
Bruce (VA) 08-12-2012 15:31:54 24.125.80.178 Report to Moderator	Re: 8n carb in reply to Hiker_64, 08-12-2012 12:56:29   " The only charger I have is a 2 amp battery tender so its going to be a while." See tip # 43. Once the battery has enough charge for the ignition, you can jump it. 50 Tips [Reply]  [No Email]
Dell (WA) 08-12-2012 09:15:14 71.217.19.188 Report to Moderator	Re: 8n carb in reply to Hiker_64, 08-12-2012 05:17:02   Hiker_64........both the Ford and M/S instructions say to set BOTH the down-pointing mainjet AND the side-pointing idlemix to 1-turn. Amazingly enuff, the engine starts but is NOT correctly adjusted. Every engine is different, howsomevers heres the way I do it. I turn the down-pointing mainjet to 2-turns and LEAVITT!!! I adjust the side-pointing idlemix for FASTEST idle, NOT SMOOTHEST idle. Understand the difference??? I then adjust the behind the carb idle-speed to extremely SLOOOOoooow 400rpms idle-speed. (ennythang under 500rpms is good) I do the idlemix-speed at least 3-times before I'm satisfied. Always for FASTEST idle-speed. The side-pointing idlemix is BASSACKWARDS, out fer lean, IN fer ENRICH. The last time I adjusted my eazy starting 6-volt 52-8N, the side-pointing idlemix was 1/4-turn and new tachometer read 438rpms. It can be done. Iff'n you don't have a tach, feel the hood vibrate. (I lay my headbone on the side of the hood) And adjust the side-pointing idlemix 1/8-turn atta time. As to whether yer M/S carb needs a rebuild, yeah probably. The instructions are NOT very good, but a careful shadetree mechanic and spray cleaner can cleaner out. The biggest problem is the little black rubber washer on the mainshaft, fingers OUT. .......Dell [Reply]  [No Email]
G6 at Snook, TX 08-12-2012 06:33:32 216.228.71.40 Report to Moderator	Re: 8n carb in reply to Hiker_64, 08-12-2012 05:17:02   If you screwed the main idle needle all the way down and did not kill the tractor, something ain't right. I haven an 8n that will run at one turn out from seated, 1 1/3, and 1 1/2. Each tractor is a bit of a beast unto itself. In this case use the manual as a guide--not an inviolable maxim. For the main needle: seated is lean, out is enriched. I have three 8n's and the idle need is somewhere bewtween 1/2 to 1/4 out from seated. After initially trying to mess with and get these tractors to idle at 500 or so rpm, I quit worrying about it. The idle needle doesn't come into play until about the 500 rpm level. The idle needle is not ornamentation, but it is rarely used on my machines. In is enrched, out is lean--the opposite of the main needle. If you have never done a carburetor before, it is a bit of a black art in addition to a science, but these Marvel carbs are't bad, I would give it a complete overhaul. "Johns Old Iron" has a good primer on how to re-work these carburetors. Look for "M/S TSX Carburetor". [Reply]  [No Email]
Bruce (VA) 08-12-2012 06:27:35 24.125.80.178 Report to Moderator	Re: 8n carb in reply to Hiker_64, 08-12-2012 05:17:02   " Question is would this carb benefit from a rebuild and if so, the basic or comprehensive? " Before you go there, try adjusting it correctly. It probably does need rebuilding, & you will know for sure if you can't adjust it. First, clean 2 of the 3 the fuel screens. (carb elbow & sediment bowl) Be careful w/ the elbow. Don't honk down on it; it's brass. First, use a flare wrench to remove the fitting. (as in the picture) Next, if you do not have another fitting to screw into the elbow (as in the picture) then use a crescent wrench on the top & bottom (NOT the sides) of the elbow to remove it. Otherwise, you will distort it & you will never get the fuel line fitting back into it. After you get the fuel screens clean, remove the bolt in the bottom of the carb bowl & make sure you have a good fuel flow. (the gas should run in a steady stream as long as the sediment bowl knob is turned on). Next, adjust the carb. Make sure the tractor is at operating temp; that usually takes 10 – 15 minutes at idle depending on ambient temp. Both Ford and Marvel/Schebler (assuming you have a M/S carb ) say to set both the side-pointing idlemix and the down-pointing mainjet to 1-turn as a starting point. I set the down-pointing mainjet to 1-1/2 turns and don't fool w/ it until the final step. Then adjust the side-pointing idlemix for fastest idle; not the smoothest idle. Next, adjust the behind the carb idle-speed set-screw for very slow 400-rpms idle. Do that idlemix adjust for maximum idle at least 3-times. Make sure that you turn the screws slowly, like 1/8 of a turn at a time & wait a second or two for the engine to catch up. Take your time! Do it like this: 1. Adjust idle mix jet until RPM increases 2. Adjust idle-mix set screw until the engine nearly stops (as slow as you can get it unless you have a tach that tells you 400 rpm) Repeat steps 1 - 3 three times. Remember the side-pointing idlemix is out for lean, in for rich. If you do not have any problems inside the carb, it is easy to get the idle down to 350 - 400 rpms. Your last step is to go back to the main jet. Remember, in for lean, out for rich. If you end up turning it OUT more than ½ turn for max power (remember, you already had it 1 ½ turns out) then stop right there because you have a dirty carb or a fuel problem. As to rebuilding the carb, I've found it to be cheaper & easier in the long run to have them rebuilt. That's because the kit will run $50 or so, plus the cleaner. And most kits do not contain throttle bushing which you usually need. GB in MT on this board does them; if he's booked up, these guys do 'mail order' work; give them a call to get a quote & shipping info. And, they also do brakes, starters, generators, water pumps, clutches, etc. Automotive Manufacturers Incorporated 2400 N Lombardy St Richmond, VA 23220 (804) 321-6861 50 Tips [Reply]  [No Email]