Hello,
New member here with little experience with small engine recreational vehicles. I traded a 1992 Subaru Legacy wagon that came with a short sale house I bought for a beat up go-kart with a Honda GC160 which leaks oil out of the crankcase (?), and a beat up DB30 with the stock Rato 79cc engine.
I plan to sell the go-kart, sell the Rato engine, and put a larger engine on the DB30 for commuting to my local job.
I found these for $99.95 new on Ebay and Amazon:
I bought two due to the low price. According to this video (same engine with an airbox), the block has nice thick webbing and walls, ball bearings for the crank (double? Only one on each side, it looks like), and a fairly standard cross-flow non-hemi head. I figured Briggs and Stratton is probably a bit more rigorous in quality control and design for their OEM suppliers than Harbor Freight.
The plan is to install the stock engine on the bike (with an air cleaner) to get the thing moving, and build the spare engine to a stage 1 or mild stage 2, something in the 12-15hp range, with an additional $100-200 upgrade budget.
Completely blueprint engine, find as much "free" hp as possible. Any tips where to start?
I would like to determine if the crank is forged. A forged crank is listed in the specs for their XR line of extreme-duty engines. If not, could I replace it with a crank from their XR1150 250cc engine? I'm not sure at what displacement things besides the bore and stroke start to change as far as parts interchangeability goes. If not, are there any sources for forged cranks with a 55 or 56mm (or more?) stroke? Billet is out of budget. At what stroke does the bottom rod end or the crank begin to interfere with the block? Different for every clone OEM?
What prep should be done to the rod? Just flash and sharp edge removal? Is it worth replacing with a billet rod for non-racing applications? I won't be WOT most of the time, but I do plan on adjusting the governor to a higher redline. Are there more rugged brands than others? Casting numbers to look for? Are some clone rods longer than others, or with different piston pin heights?
I'd like to reduce the reciprocating mass as much as possible. Are there balancing pads on the rod and piston that I can grind? Shave the counterweight? Most automotive applications try to to reduce oil splashing, do I wan to try to increase it, or at least keep it the same?
Are there Clevite bearings for these engines? ARP fastners? Is that overkill for small engine builds?
I would also like to swap the dished piston for a flat top hypereutectic. Are they readily available? Chromeoly rings, preferably a gapless design like Total Seal . Polish cylinder walls with a 3M green or blue pad.
Replace valves with flat faced, preferably with narrow stems in the port area. Sources? Bronze valve guides, stiffer springs (how stiff?), polish lifter faces, polish combustion chamber, polish exhaust runner, thin head gasket, lightweight pushrods, roller rockers, ratio is dependent on final cam selection, which is dependent on max RPM, which hopefully will be determined here! I need to know it to determine header length and intake runner length as well.
I have been looking into the high compression 160cc (?) head, and I wanted some opinions about it. I feel that the increased CR would be better than the larger valves and lower CR for torque vs top end VE, which isn't as important in my application. I have also been looking into meth injection to combat detonation. Has anyone tried it?
In this video, he recommends partially filling the top of the head where the valves are with epoxy for stiffening. Made sense to me, what do you think? The ports are relatively straight as they are, what are areas to work on? How much of the valve guide and bosses can I remove without reducing rigidity and strength? Has anyone tried raising the port floor with epoxy? How much is a three angle valve job for these heads generally? Do you gasket match ports?
What carb and throttle body diameter would be a reasonable choice for this build? What affordable brands have served you well?
I was leaning toward a Maxtorque SS clutch, again stall speed being power band dependent. Seem reasonable? Any info on determining the ratio for the clutch and the drive sprocket? Tires will be 15x6-6
I haven't started looking into the ignition or the flywheel yet, any leads or ideas in that realm would be very helpful.
Thanks in advance!
New member here with little experience with small engine recreational vehicles. I traded a 1992 Subaru Legacy wagon that came with a short sale house I bought for a beat up go-kart with a Honda GC160 which leaks oil out of the crankcase (?), and a beat up DB30 with the stock Rato 79cc engine.
I plan to sell the go-kart, sell the Rato engine, and put a larger engine on the DB30 for commuting to my local job.
I found these for $99.95 new on Ebay and Amazon:
I bought two due to the low price. According to this video (same engine with an airbox), the block has nice thick webbing and walls, ball bearings for the crank (double? Only one on each side, it looks like), and a fairly standard cross-flow non-hemi head. I figured Briggs and Stratton is probably a bit more rigorous in quality control and design for their OEM suppliers than Harbor Freight.
The plan is to install the stock engine on the bike (with an air cleaner) to get the thing moving, and build the spare engine to a stage 1 or mild stage 2, something in the 12-15hp range, with an additional $100-200 upgrade budget.
Completely blueprint engine, find as much "free" hp as possible. Any tips where to start?
I would like to determine if the crank is forged. A forged crank is listed in the specs for their XR line of extreme-duty engines. If not, could I replace it with a crank from their XR1150 250cc engine? I'm not sure at what displacement things besides the bore and stroke start to change as far as parts interchangeability goes. If not, are there any sources for forged cranks with a 55 or 56mm (or more?) stroke? Billet is out of budget. At what stroke does the bottom rod end or the crank begin to interfere with the block? Different for every clone OEM?
What prep should be done to the rod? Just flash and sharp edge removal? Is it worth replacing with a billet rod for non-racing applications? I won't be WOT most of the time, but I do plan on adjusting the governor to a higher redline. Are there more rugged brands than others? Casting numbers to look for? Are some clone rods longer than others, or with different piston pin heights?
I'd like to reduce the reciprocating mass as much as possible. Are there balancing pads on the rod and piston that I can grind? Shave the counterweight? Most automotive applications try to to reduce oil splashing, do I wan to try to increase it, or at least keep it the same?
Are there Clevite bearings for these engines? ARP fastners? Is that overkill for small engine builds?
I would also like to swap the dished piston for a flat top hypereutectic. Are they readily available? Chromeoly rings, preferably a gapless design like Total Seal . Polish cylinder walls with a 3M green or blue pad.
Replace valves with flat faced, preferably with narrow stems in the port area. Sources? Bronze valve guides, stiffer springs (how stiff?), polish lifter faces, polish combustion chamber, polish exhaust runner, thin head gasket, lightweight pushrods, roller rockers, ratio is dependent on final cam selection, which is dependent on max RPM, which hopefully will be determined here! I need to know it to determine header length and intake runner length as well.
I have been looking into the high compression 160cc (?) head, and I wanted some opinions about it. I feel that the increased CR would be better than the larger valves and lower CR for torque vs top end VE, which isn't as important in my application. I have also been looking into meth injection to combat detonation. Has anyone tried it?
In this video, he recommends partially filling the top of the head where the valves are with epoxy for stiffening. Made sense to me, what do you think? The ports are relatively straight as they are, what are areas to work on? How much of the valve guide and bosses can I remove without reducing rigidity and strength? Has anyone tried raising the port floor with epoxy? How much is a three angle valve job for these heads generally? Do you gasket match ports?
What carb and throttle body diameter would be a reasonable choice for this build? What affordable brands have served you well?
I was leaning toward a Maxtorque SS clutch, again stall speed being power band dependent. Seem reasonable? Any info on determining the ratio for the clutch and the drive sprocket? Tires will be 15x6-6
I haven't started looking into the ignition or the flywheel yet, any leads or ideas in that realm would be very helpful.
Thanks in advance!
