1984 D50 Carb help/Q's

[CowBoyRoy81]

Hello,

New to the site and Might Max/D50's. But I have some questions in regards to the carburetor that I was hoping someone on here who's knowledgeable with these factory carbs can help me with.

Background: Original/Stock 1984-D50-G63-Manual-2wd-80k miles I bought off my grandpa for $100 a few years back. She's sat for 10-12 years so I immediately changed fluids, filters, plugs, wires etc etc. Got her tag'd and registered and insured. Drove about 500 miles since road worthy again. My background is 10 years as a diesel mechanic in the Army, grew up Mopar or No Car and know Carter/Edlebrocks and Holley's inside and out. Currently a service writer for the local Cat dealer. I state this because I'd appreciate if the trolls and bench racers didn’t' chime in with smart ass remarks. I'd rather not just slap a new carb on it. I'm sure it's a minor issue just looking for guidance in unfamiliar territory. If I can save a little $$ by doing myself and gain some knowledge then that's what I'm going to do. Truck will be/is daily driver when not riding motorcycle or winter 4x4 is needed. I did search the forum and the net and asked around work but these carbs seem to be alien to most people.

Issue: The carb has what I call a "flat spot". It's right around where you'd have the RPM's to engage the clutch. To get going you simply over rev a little bit and the issue is gone. While driving at speed or down shifting the problem is minimal. The temp of the engine and ambient temperature do effect it but not in the manner of it being a choke problem. That works fine it's just harder to push through that "flat spot" when the engine is cold which means higher RPM's to shift. The mechanical fuel pump did go out a couple years back and that's when it really got parked by my dad. I slapped an electric fuel pump on it and she's working great....except this "flat spot", which I feel like it's leaning out.

So knowing all this I'm asking if anyone has had a similar issue? Rule out fuel pump or air delivery. WOT works as well. I do have a rebuild kit for the carb and after researching on here I'll do the Cigar smoke vacuum leak first. Then start with the accelerator pump and.......? Also I have no doubt in my mind the ignition problem is fine overall because at all RPM's she runs great. I do understand the vacuum somewhere could effect timing. And this is an example of knowledge I'm trying to gain. It feels and sounds like a lack of fuel though, not timing/advance/retardation......he he he

Thanks for your time and any help you can provide.

Oh here's a picture of "Little Blue" for ya, sometimes dubbed as the "Blue Bomber"

http://www.mightyram50.net/vbulletin/attachment.php?attachmentid=10548&stc=1

Willie

[ragragtimetime]

welcome! & sweet ride...made me smile when i saw the cap http://www.mightyram50.net/vbulletin/attachment.php?attachmentid=9248&thumb=1&d=1397385874
i assume you changed air filter (but if not rockauto is a favorite around here 2286565420978579 discount code expires on August 10, 2014). i am having a little trouble fully understanding "flat spot" (i am a 1st gen guy with zero training but have been tinkering for decades) does it go away as it warms up? could be choke needs to be adjusted to open sooner by 1 tooth (towards the firewall, use stubby phillips) does it blow black smoke til warmed? (may have wrong plugs, for a g63b "the" mitsubishi manual says should be BPR6ES-11 or W20EPR-U10). what is the current condition of plugs? where is the temp guage when fully warmed? should initially go up slightly above half then stay slightly below half (may have worn/wrong thermostat...for g63b "the" mitsubishi manual says should be 88c/190f or more...must have a "jiggle valve" on thermostat to allow antifreeze to pass & get to wax element in carb so choke will open). check for worn linkage, smooth throttle operation, worn/loose vacuum hose connections (issues change/occur @ various times as engine warms), check choke for fully open & fully closed positions (may stick causing other linkage to not operate), sub egr also will cause linkage movement issue (& is very easy to clean...just don't drop any of those tiny pieces). i use gumout spray "carb + choke cleaner" (& would not hesitate on using most of the can) as it will clean & not leave oil residue that may accumulate dirt & cause it to be cleaned again (i have a long gravel driveway). i you feel the need for lubricant i recommend a "dry graphite lube spray" instead of petroleum base. best of luck!...& want more pics!

[ratesheet]

Hey...CBR81....I'll throw in my 2 cents as I had a similar issue....mine is an 86 Ram 50 G63B 5sp 2 wheel drive...picked it up for $100.00 not running and and sat non opped for 5 years....I also had a flat spot accelerating, I have no tach but I'll guess it was about 2,000 rpm...off idle fine, WOT fine, it just fell flat at about 2,000 rpm...had it tuned up by a shop for smog (which it passed) but it still had the flat spot when accelerating, then the distributor died...got a reman dist. could not get it timed to save my tail...TDC was the best I could do at idle...took it back to the shop they could not get past TDC at idle either...then the mechanic pulled the dist. ignored the marks on the cam gear adjusted the cam (advanced) reinstalled the dist, the truck runs fine now...no flat spot, no pinging, pulls very smooth all the way through the rev range...hope this helps in some way, good luck

[geezer101]

I'd head for the usual suspect on the Mikuni carb - the secondary vacuum can (the round vacuum actuator on the side of the carb that is attached to the secondary throttle shaft linage. With the engine off and the air filter removed, disconnect the small vacuum hose that is connected to it (a small elbow shaped hose). Connect a longer vacuum hose into the top vacuum barb on the actuator and open the throttle all the way, then apply vacuum to the attached hose. If it pulls the secondary linkage open and holds the vacuum then it's serviceable. Normally the diaphragm inside the vac can splits, causing an air bypass and killing mid to top range power.

[BradMph]

I was going to say it was Muffler Bearings. :lmao:

[pennyman1]

2nd on the secondary vac can - common fail on these carbs. The egr and sub egr should be cleaned regardless as that system crudded up will cause all kinds of issues.

[CowBoyRoy81]

Hey All thanks for the replies! Sorry, it’s been this long since I’ve been on. This is a managable issue but it’s mainly annoying and in the dirt/rain it’s a one-tire-fryer since I have to over-rev for the clutch, but don’t want to burn the clutch at the same time.

Ragragtimetime: I have used RockAuto for most of what I’ve gotten so far. Except I get a killer discount at Napa so will usually get common items there. But the shocks and filters I did get there. Also many parts for my other projects. To answer your questions this little beast blows no smoke at any RPM or speed in any weather. Runs like a complete champ. By “flat spot” it seems as if during the power band it either leans out or runs rich for just a little bit until I throttle through it. Due to no smoke I believe it’s a lack of fuel at that rpm (also no tach).

Ratesheet: I hadn't driven it for a while (motorcycle season) but drove her today for the first time in a while. And I decided that with the upcoming oil change and checking of the rest of the fluids I’m going to check timing and inspect the distributor. I did change plugs & wires but know timing can be a PITA. So will grab the old timing light and see what happens.

Geezer101: I’ll be doing this tonight…..I truly believe it’s an issue with a vacuum line but have no knowledge, but I’m going to print off this thread and take it home and give it a shot tonight. I do have a rebuild kit for the carb and if the lines don’t fix it I guess I’ll take a thousand pictures while disassembling because I’m afraid I’ll cross a line while re-installing. But my other thought is if this vacuum line doesn’t do it then I’ll slowly dis-assemble while on the truck and inspect diaphragms and such. I hope it’s a line though!

But since this post I have additional done the following and none has helped the issue:



Muffler was disassembled and the bearings checked out. Didn’t forget the horn bearings either!
Blinker fluid was flushed out and replaced.
Took an exhaust sample and sent it in.
Fed the hamsters in my differential that keep the thing rolling. Can’t let them starve!
Put my 17month old boy in coveralls and a gas mask with a K-bar and sent him under the truck to find the gremlin who I think is responsible for this issue. Boy came back, mission failed…..
Filled my tires with helium hoping to lighten my overall weight allowing for better MPG and efficiency
Installed a red “GO FAST” Button on my dash. Couldn’t figure out what to hook the wires to, but it looks cool


;)

[CowBoyRoy81]

Hey All thanks for the replies! Sorry, it’s been this long since I’ve been on. This is a managable issue but it’s mainly annoying and in the dirt/rain it’s a one-tire-fryer since I have to over-rev for the clutch, but don’t want to burn the clutch at the same time.

Ragragtimetime: I have used RockAuto for most of what I’ve gotten so far. Except I get a killer discount at Napa so will usually get common items there. But the shocks and filters I did get there. Also many parts for my other projects. To answer your questions this little beast blows no smoke at any RPM or speed in any weather. Runs like a complete champ. By “flat spot” it seems as if during the power band it either leans out or runs rich for just a little bit until I throttle through it. Due to no smoke I believe it’s a lack of fuel at that rpm (also no tach).

Ratesheet: I hadn't driven it for a while (motorcycle season) but drove her today for the first time in a while. And I decided that with the upcoming oil change and checking of the rest of the fluids I’m going to check timing and inspect the distributor. I did change plugs & wires but know timing can be a PITA. So will grab the old timing light and see what happens.

Geezer101: I’ll be doing this tonight…..I truly believe it’s an issue with a vacuum line but have no knowledge, but I’m going to print off this thread and take it home and give it a shot tonight. I do have a rebuild kit for the carb and if the lines don’t fix it I guess I’ll take a thousand pictures while disassembling because I’m afraid I’ll cross a line while re-installing. But my other thought is if this vacuum line doesn’t do it then I’ll slowly dis-assemble while on the truck and inspect diaphragms and such. I hope it’s a line though!

But since this post I have additional done the following and none has helped the issue:



Muffler was disassembled and the bearings checked out. Didn’t forget the horn bearings either!
Blinker fluid was flushed out and replaced.
Took an exhaust sample and sent it in.
Fed the hamsters in my differential that keep the thing rolling. Can’t let them starve!
Put my 17month old boy in coveralls and a gas mask with a K-bar and sent him under the truck to find the gremlin who I think is responsible for this issue. Boy came back, mission failed…..
Filled my tires with helium hoping to lighten my overall weight allowing for better MPG and efficiency
Installed a red “GO FAST” Button on my dash. Couldn’t figure out what to hook the wires to, but it looks cool


;)

[CowBoyRoy81]

Wait,

BradMph you're in Spokane?