gx620

T

Time Bomb Tom

Member
Was given a gx620 Honda engine. I plan on putting it on a buggy and just wondered what performance parts are out there for it. Will any of the smaller big block parts swap to it, like from the gx390? Just curious.

thanks
 
The lack of replies is not making me hopeful. So will the standard big block hd springs fit this thing at least? If I pull it apart, clearance the rods, install some better springs and remove the governor, how many rpms will it safely turn? I'm going to have to build a carb adapter so I can install a spare Mikuni I have laying around since this came without the carb and linkage. Any thoughts or suggestions are appreciated.
 
I am not sure, but the 620 is a 2 cylinder that probably shares many parts from the smaller single cylinder honda. Check the bore size,valve size and crank size. Big block billet rods would be at the top of my list in order to turn more r's. I have a 620 also that was in a service truck, a rod let go of the crank and put a hole in the block. Cool motor with pressurized oiling system and filter. I seem to remember the push rod system was rather odd and the flywheel weighed a ton.
 
Any idea on where to get billet rods and a flywheel? Doubtful that 340 or 390 rods would work due to having a dipper and the 620 is pressurized. 5000-5500 rpms is the max I want to turn it. What kind of torque convertor would work on this engine?
 
You could cut the dipper off. I would check with ARC racing, They also may know of others that mod the twin honda.
 
dipper rods fail at high rpms because they have crappy lubrication properties. The gx620 is pressure lubed. You can safely turn them 5500 rpm no worries. As far as the head goes, just looking at the head alone, they look very VERY similiar to the gx340/gx390 heads, so Id say you could probably slap on some HD single rate springs, jet it a bit, get a high flow header (possibly weld it yourself), and youd have some good mods.

A lot of guys that run them on mini buggys use the comet 780 series torque converter. If you run a 40 series (esp the knock off version) you may end up chewing up your belts and have some issues with that much torque. Again, depends on what you are putting it on.

there are relatively new predator 670 performance parts coming out. Might want to give them a call about your 620, I know for a fact that the CAMSHAFT is the weak link here (e.g. plastic).
 
thanks for the insight. I contacted ARC already and they don't have any parts to fit it. I'm wondering if I should just shim the springs or go with the HD's. If the gears are plastic, would the HD's be too hard on them?
 
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