Top end rebuild

Brenson

New Member
I have a 1990 2-stroke 3pg EZGO cart recently purchased. After replacing the voltage regulator for a charging issue, I have now discovered another problem. The cart seems to die on hill climbs and now has got to where it moves very slowly forward or backward and eventually won't move at all even though the engine seems to be putting right along. What I have checked or replaced so far, besides the VR, is a new battery which meets the carts cca requirements, I've drained the fuel tank and added fresh fuel mix in accordance with the ratio recommended in the manual(the automatic oiling system has long since been bypassed according to the PO). It has good spark at the plug and I've tested the compression at wot. It has 95 in fwd and 85 in rev. So I'm figuring on a top end rebuild first of all since it will need that regardless of whatever other problems might also exist. Does anyone have any advice for me which might be helpful before I begin? Should I pull the engine to do this or can it be done just as well in frame? Any other checks or components I should look at given the situation I've described? Thank you very much.
 

Brenson

New Member
OK, thanks. I was kinda figuring on that...plus it would be easier to check other things like the clutch assy I suppose. My plan is to leave the bottom end alone since I haven't detected any problems down there unless good judgment would say I ought to freshen up that part too while I'm right there??
 

Brenson

New Member
Well, after numerous delays...several months in fact!, I've finally got down to the nitty gritty on this EZGO cart. What I ended up doing is installing a top end kit(cylinder, piston, ring set and all related gaskets) and while engine was out replaced both crank seals even though the old ones appeared dry. There did not appear to be any side play in the crank bearings so I didn't go any further into the case than the seals. Since I now premix the fuel, I removed the oil tank, lines and the related linkage on the front of the engine cover. I have a fresh tank of 128:1 fuel in the tank and installed a new carburetor. Now, only the starter is spinning the thing over and the engine doesn't fire. Have a good blue spark at the plug and have confirmed adequate fuel delivery. I checked compression and only get 70-75psi in fwd or rev. I pulled the exhaust pipe loose to make sure I didn't reverse the piston on the install(I didn't), and a considerable amount of fuel ran out of the exhaust port and the L-shaped exhaust pipe I removed. Perhaps running way too rich? If so, what might be the cause? Wondering also if I might have broken a piston ring on the install. The cylinder was tapered and I used a bit of 2 cycle oil to lube the cylinder before installing and it appeared to go in the cylinder relatively easy so I'd be surprised if it did break a ring. Anyone have any other thoughts what might be going on with the low compression and oily exhaust right after a top end j0b was done. I had about 90 psi before and it ran fairly well despite that, but doesn't run at all now. What might I have done? Any thoughts would be appreciated!
 

Nubs

Cartaholic - V.I.P.
My first guess would be that perhaps the piston went in the wrong way, 125 to 140 lbs is where it should come in at.
 

Brenson

New Member
I went ahead and pulled the jug...piston was installed correctly with ports facing intake side and rings were fine. I noticed a good amount of drag as I lifted the cylinder off the piston...a good snug fit appears, nothing like the old cylinder and piston which had a bunch of slop. Yet I started with about 90 psi compression with the old piston and cylinder and now with new, snug top end pieces, I get just 75. Something doesn't add up. I've done something wrong and can't figure out! The top head gasket was perfect condition as was the gasket between the case and the jug...all bolts were still tight as I had torqued them. The one thing that seemed a little odd to me, was that despite the exhaust port and reed valve area being flooded with fuel before I tore it back down, once I removed the jug, the crankshaft, rod and the entire crankcase area seemed dry as a bone. I haven't a lot of experience with 2 cycles, but I'm used to seeing at least a slight coating of lube or something in that area. Maybe 2 cycles are different? Even though I had replaced both crank seals the first time around, I previously had tried spraying the carb cleaner trick around them while cranking it over and it really changed nothing. I'm now completely stumped! Any other thoughts would be appreciated.
 

Nubs

Cartaholic - V.I.P.
Are You checking the compression with carb butterfly wide open, like holding it open with Your hand?
 

HotRodCarts

Cartaholic
Another thing I noticed you mentioned you wiped 2 stroke oil on the cylinder when you assembled the engine. Did you oil the rings up before installing?
 

Brenson

New Member
Nubs: I checked compression at varied throttle positions and not much difference at any point, perhaps at WOT it was slightly higher but not much. Wondering about the reed valve assy...that was another part that I had touched during the top end job...could I have installed it upside down? It appeared the same either way and I didn't make note of which way was up on the disassembly.

HotRod: Yes, I covered both the cylinder bore and rings with a light coat of 2 cycle oil. Now the rings didn't have any markings on them indicating direction, but they both appeared to have a slight bevel on one side, so I installed with that side up based on the information I've read here on this site.
 

Brenson

New Member
I've checked a few more things and I need to correct one thing I mentioned earlier. I had said the crankcase area was dry as a bone...well, not quite. After removing the piston from the rod, I could see down in there a lot better and actually there is a fair amount of fuel standing on the bottom of the crankcase halves. I had presumed everything dry initially, but I was just seeing the rod and top side of the crank and apparently after sitting a few days, likely everything had drained to the bottom of the case. So I'm wondering first of all, it is normal at anytime for there to be that much fuel in the crankcase that you can see it standing in the bottom? So combining that with all the fuel that poured out of the exhaust pipe and reed valves, I'm wondering if the rings have simply not seated yet at all? I checked the end gap for the rings and they measure right at the max spec of .016. I did lightly coat them and the cylinder prior to piston install...so perhaps what I thought was a light coat might have been too much? I've also heard war stories of cheap third world parts, perhaps that is the situation here pertaining to the top end kit I ordered off ebay. I always believe that when you work on something and you end up with a problem you didn't have to begin with, I feel it is either an error(s) in something you did on the reassembly or it is some kind of defective part. So that is what I'm focusing on...any suggestions?
 

Brenson

New Member
I took my cylinder, piston and ring set to a local machinist today to have everything miked and the clearances checked. He said all was good to go on that. He has a good bit of background in 2 cycles(which I don't) and shook his head when he was asking me about what kind of fuel pressure I have and I mentioned that I have an electric fuel pump. He thinks all the fuel gathering in the bottom of the crankcase, the fouling of the spark plug and fuel running out in the exhaust port is from the electric pump pushing too much pressure against the carb and forcing the needle off the seat and flooding. He asked me if I had a fuel pressure regulator installed and I don't. Again, I didn't have this problem before, so it seems odd that all of a sudden that would now be a problem just because I had the engine out and replaced a few things. Previously, the cart ran halfway decent, just had reduced power and smoked a lot due to the worn out rings and jug was my assumption. Has anyone heard of a electric pump causing this problem with too much pressure? The PO had told me he added that because the EZGO fuel pumps were so expensive. I have checked around and they aren't that much...at least not in the range of a freakin muffler. But I hate to keep throwing parts at this thing and coming up empty, but I would be curious to know if this is a potential problem before I run out and spend more money on a 27 year old cart.
 

HotRodCarts

Cartaholic
Yes a electric fuel pump can cause problems but some guys use them. It depends on the pump and how much pressure it puts out.
 

Brenson

New Member
I'm now thinking I may have had this problem to some extent before I did the top end repair. I've always used electric pumps with various muscle cars I've pittled around with over the years but I can see where a 2 cycle is a whole different situation indeed. I'm not going to worry about testing pressure on the electric pump, I'm just going to go ahead and eliminate it and go with the setup it had to begin with. I've ordered a replacement EZGO fuel pump and plan to clean out the fuel tank while I'm waiting and put a new fuel filter and fuel lines on it when I get the new pump. Whether that is the main and only problem I have remains to be seen, but I would just feel better having it set up as the factory made it. I'll check back if I have any problems with the new pump and getting the fuel system set up properly.
 
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