In need of safe higher rpm's

[raydhd]

The carbs on these engines work great IF both the idle jet and main jets are converted to be adjustable. I further dechocked the carb and throat matched it to a VC mikuni intake manifold as K&N air cleaner mount. With both carb circuits being adjustable you can easily with a turn of a screw dial the engine to a perfect tuned state. As far a power goes I am still lifting off the throttle @ 5600 rpms where it is still pulling hard on 24" tires with the windshield up. This is at 45.5 mph. Point #2 here if you are using the stock dished piston without milling the head your CR ratio is about 8:1. That was the whole reason VC came out with the long rod flat top piston combo to get the compression ratio up without milling the head. Even the 69 mm cranks purpose over the 440's crank was not for displacement but to get the CR up with the dished piston.

[sho305]

I have a home depot 420. I ran it years with ported and cut head, different carbs, header, timing key, hd springs to 5200 rpm. But in normal riding I rarely went over 4500, above that was only a short blast. When I took the rod out it had some discoloring on the cap, or in the cap rather. I put the vegas long rod in and cut about .100 off the piston, which is pretty much a few thou more than the dish was. I went to a thick head gasket since the piston is now about deck height and no dish anymore. I only cut the head .050 to start with because I only run regular fuel. Put the cheater vegas cam in and it runs stronger for sure, it revs hard and pulls past 5K like nothing. I also put chromo pushrods in, NR shaft rockers 1.3 ratio, cap on both stock valves, the seats under both springs. Its still running great but I have had the loctited bolts come loose in the block cover, so yes the 10 bolt block is worth it. I have a stud kit for it I have to put in. The VC460 was a great deal, it has the 10 bolt and almost everything I have, just need the rockers and the head worked on.

[raydhd]

Yes I also am running the .065 head gasket with the zero deck flat top piston and .075 milled head. With the shorter stroke Omega build I wonder if the .045 head gasket would be better ? I can't seem to find the .065 gasket for sale anymore.

[sho305]

My original lifan gasket was a thin copper thing, I mean thin. If I had a performance engine only I would run a lot of compression and premium fuel, or what premium will support for compression. I run this cart for yard work and all that and while it does not take that much fuel I would have to buy premium special for it and maybe be someplace in the sticks I could not easily get it without a trip to gas station which I didn't want. I think I have the .065 too and never looked it up, but without the dish I knew it would be higher than before and .050 cut was said to be max for regular or so I was told, so I swapped to the thick gasket to lower compression.

What I ran into is these kart guys who race they buy a can of fuel and race that is all they do. They run high rpm and don't care about durability for the relative few hours they run them. Which is great but I expect years of service from my cart and run any gas I have laying around lol. If i had a second cart for fun that took premium that would be fine, but I don't have another cart yet.

[Notsoezgo]

Well so far my engine shipping has been delayed, when it gets here I'll run it to make sure it is ok then go from there. I am thinking governor and oil sensor delete 4.410 billet Rod with stock piston billet flywheel champion 1:1 rockers with chromoly pushrods (6.74) high torque cam and 34mm carb thoughts? I may also try my hand at porting polishing.

[raydhd]

IMHO I would use the stock carb with an adjustable main jet. The 34 mm is really racing high rpm spec. The second part of that is it will take quite a bit of linkage work to make it work. You haven't burnt any bridges starting with the stock carb and if you decide you are under carbed the 34 mm can be added later after you have the whole engine swap whatevers completed. These engines respond well to clearing out the valve pockets and unshrouding the valves along with the cleaning up the area around the valve guides.

[Notsoezgo]

Originally Posted by raydhd

IMHO I would use the stock carb with an adjustable main jet. The 34 mm is really racing high rpm spec. The second part of that is it will take quite a bit of linkage work to make it work. You haven't burnt any bridges starting with the stock carb and if you decide you are under carbed the 34 mm can be added later after you have the whole engine swap whatevers completed. These engines respond well to clearing out the valve pockets and unshrouding the valves along with the cleaning up the area around the valve guides.

I like your ideas on stock carb with adj main jet. My other Duromax 440 has VC's 3 circuit carb it runs well and idles slow. Hardly ever choke it. I'll look for an adjustable main for the stock carb and try that first. Not sure who has it

[raydhd]

ECcarbs sells them along with NRracing. Last I looked EC was cheaper. EC part # 169F-43G390

[Notsoezgo]

Originally Posted by raydhd

ECcarbs sells them along with NRracing. Last I looked EC was cheaper. EC part # 169F-43G390

Thank you I may just give that a try, so this adj. Jet is inside the fuel bowl and you drop the bowl for adjustments I presume

[Notsoezgo]

Originally Posted by raydhd

ECcarbs sells them along with NRracing. Last I looked EC was cheaper. EC part # 169F-43G390

Thank you I may just give that a try, so this adj. Jet is inside the fuel bowl and you drop the bowl for adjustments I presume