MTD off-road build (Mobile Terrain Dominator) "2"

Pulse line in good condition?

Yeah, I actually just had it off today to get to the PCV assembly. No holes in the line or anything.

Flywheel key ok?

Yeah, I checked that a couple of times a while ago and it was still good.

Does is fire right up with starting fluid? that could help narrow it down to either a fuel or spark problem. maybe you have some rare problem with the magnet on your fly wheel? Maybe low compression?

No I've tried ether in the carb while cranking and that doesn't help it, but when I check for spark it's there. Maybe it's not strong enough under compression though...

Sounds like MTD and Red has the same issues as I have mentioned in the past.  It is worse when cold.  Also like you experienced, changing plugs will make it run again fine sometimes for a little while.  

On mine I have checked everything like you.  It's almost like a gremlin in the system.

if it wont run on starting fluid, you have a spark problem, back before the wheel horses, we messed with all kinds of tractors, and any oppy we had always seemed to have spark problems sooner or later. and most all of them loved to foul spark plugs. had 3 or 4 that would loose spark after the coil got warm, but only if you shut it off, say it was cold, it would start right up and run all day. unless you shut it off, then no matter how much you cranked or worked on it, it wouldnt start. until you let it cool clear back off then start right up. How are you setting the gap on your mag? and are you getting a big fat white spark or a little blue or purple spark? is the spark going to same part of the spark plug or dancing around to a differnt part of the spark plug each time? If it was mine Id put a new, not "good" used, coil on it. and a brand new set of plugs

Just FYI Ive been fooled by weak spark many many times, and replaced expensive parts, cleaned carbs etc everything but spark plugs and coils and only figured it out the hard way. on more than one occasion. had a quad that would rattle the choke a tiny bit closed and foul the plug without me knowing. left me stranded and I went home from a big riding trip because I couldnt figure it out, because I checked and it had spark. well guess what got home and after bunch of other diagnostic work still wouldnt run. was gonna scrap the quad but just for the hell of it put a fresh plug in it and it fired right up. also had me and a couple buddys gx390 foul a plug every couple of years just randomly, same thing, good spark but wont run. new plug fixes it. also I dont think brand really matters but I only run NGK and have had very good luck with them

I forgot i had a coil like that. Would start cold and run as long as you want, but if you shut if off and tried to start it while it was still hot you couldn't spin it fast enough with the starter for it to make spark. That engine doesn't have that issue anymore though, as I've replaced the coil.

Oh a had a brand new coil on 'er, that didn't fix the issue and new plugs didn't either. Unfortunately. Also mine never had the hot starting issue. When I could get it running, I could drive it around for a half hour or so, shut it off, and it would start right back up again if I hit the key. But let it sit for maybe 15 minutes and forget about it. No starting at all.

Like Might said, definitely a gremlin in the system. So I decided to remove said gremlin today:



Yepper, time to move on. For a while anyways. I can mess with the pressure lube model 40 whenever I feel like it now, but without having a dead tractor.

Got my 18hp model 42 out to prepare it to go in the tractor.



Got some stuff put on it. Put the original carb back on it, and used the brand new coil that was on the pressure lube engine.



Everything hooked up, filled with oil, and grille back on.



First start!



Had an issue with the throttle not working properly, but I got that fixed and it works perfectly now.



Did some wheeling... She runs good! Had to tweak the carb mixture a bit to get the throttle response better, but it's a good running unit now.

So yeah...kind of a bummer that the pressure lube opposed is out, but it ain't the end of the world. Or the engine, haha. I'll get to it again someday, for now I'm just glad to have the MTD back!

Not sure if @AllisKidD21 is having the same issue... but what about cold hard start until it gets warm then it restarts easier?

I would've tried swapping the intake from the splash onto the pressure lube myself (probably ruining both engines in the process). Nice you got it running though!

I've wondered if it were a compression issue on mine.  I need to check it cold then again warm on mine. Possibly a valve adjustment.

Yeah I'm sure there's a few different things I could've tried, but I just got so tired of tearing it apart and changing things with no success that I couldn't find the motivation to work on the bigger any longer. I can still mess with it to get it running though! I just don't have it in the MTD anymore.

AllisKidD21 wrote:

Yeah I'm sure there's a few different things I could've tried, but I just got so tired of tearing it apart and changing thing with no success that I couldn't find the motivation to work on the bugger at all. I can still mess with it to get it running though! I just don't have it in the MTD anymore.

I understand man... Especially since you have a spare engine ready to go. I need to work on getting the 2 others I have running.

Nice. I'm thinking about throwing my pressure lube back together for a while to see what it acts like myself.

So Allis, any upgrades planned for this thing anytime soon?

And did you ever get the rims painted?

Here's an idea, might not be the case here, but what if something screwy is going on with your kill switch.  The switch might only be meant for 12vdc, but if you're using it as a kill switch it has to break a much higher AC voltage.  Maybe the high voltage is jumping across the switch contacts giving you a gremlin spark problem?  This idea doesn't make a ton of sense for you because once your engine is warm you don't have this problem.

I tried it with the kill wire unplugged from the coil a couple times.

Anyways I've been driving 'er around a bunch this morning:



Running great! Sure is nice to be able to hop on and drive 'er whenever I want. You can see the exhaust collector I made for it as well. Sounds pretty cool and keeps the flames down, haha.

Glad to see it back in action

Thanks CC. I sure am too, haha.

Nice action shot

Thanks Carl. With every romp, ya gotta take at least one picture.

AllisKidD21 wrote:

Thanks Carl. With every romp, ya gotta take at least one picture.

That's a good thing to keep in mind!

Bonus points for pictures with the tractor topside bottomwise

Well boys, I gotta say the splash lube model 42 just wasn't doing it for me. After using it for a while I noticed it didn't run as good as I first thought. Had a weird stutter/cough that it did when you punched the throttle, and I couldn't seem to be able to tune that out if it. Also I think it had a bad exhaust valve seat or something on one cylinder... it just wasn't great in general.


As some of you may remember I picked up another pressure lube opposed a little while back. It was actually seized when I got it, and once I got it all cleaned up and spinning over good enough to start it, I ran into what turned out to be carb troubles. So unfortunately the ol' MTD has been sitting for a really long time..... But today I finally went at it and got it starting and running good!



Oh yeah, she lives!!!









Definitely VERY happy, I was starting to think she'd never run and drive again!

Here's the new mill:





18hp model 42. Runs great! I've started it cold and hot a few times while messing with other stuff, and it sure seems to start fine too, so hopefully it'll be pretty reliable. Seems to have lots of power too. It has great low end power just like it should, so I'm thinking it's pretty healthy still.

Super happy to have my main mean machine back, that's for sure, hahaha. Let me know what ya think!!