Questions before commercial production

Mr. Minecraft · Jun 15, 2013

Hey everyone,

I am going to be producing 2 stroke bikes for a profit this summer, and need some input on a few things before I start.

1. I am replacing the studs and hardware, but what can I do to keep the studs from bending outward when i tighten the nuts down on my bike?

2. Can i replace the studs with long hex bolts (or something similar)?

3. What's the best way to clean out the gas tank before I use it since they often have rust or dirt in them? I was thinking to put a bunch of bb's in there with some acetone and shake it for 5 minutes, then rinse it out.

4. Is it worth the effort to take off the head and cylinder and sand the 2 surfaves to make them flush and raise compression a bit?

I am sure i will have more questions as i build.

Thank you,
Christopher

usflg

Greg58 · Jun 15, 2013

If you are going to do things right you will need a sand blaster for the tank, a friend has one with a wand thats small enough to go in the tank opening. If studs are bending alignment is the issue, frame angle verses engine mount sometimes are not the same. If it were me I would disassemble each engine and check for problems, if you use engine kits that the seller advertises has been ran you can look for leak areas on the head or cylinder. Grade 8 hardware of good quality would save you some headaches.

mew905 · Jun 15, 2013

bending studs is as easy as replacing them with high grade steel. My OEM studs bent out but the new ones from the SBP kit havent. You CAN replace them with M6 hex bolts, I did it with my front mounts because the studs were too long and wouldnt allow a flush (ish) mount. If you're replacing the studs, then you can remove the old ones with some locking vice-grips (or pliars if you have a robot grip, as far as I can tell they're blue-loctited in). Or you can double-nut the studs and by unscrewing the inside (lower) nut, it'll lock against the upper nut and take the stud out.

You can buy good hardware from SBP (or the hardware store but it doesn't look as pretty). Head studs on a 66cc are almost always standard M8 threaded stud (thats 1.25 pitch, make sure for sure you get the right pitch, I ordered the wrong set by accident...). It looks like its just cut from a threaded rod. SBP also offers a thinner head gasket should you wish.

Yes, lapping the head will help reduce blown head gaskets by spreading the pressure more evenly as well as improving compression.

I'm trying to find the oil seals for the 6202 bearings other than stock OEM ones, as far as I can tell, RSE are the only ones who sell something other than stock, but when you order them, order two and put in the notes you need both sides. the RSE graphite gaskets are great too, soft enough to produce a good seal.

But ordering all this stuff individually will cost more than alot of people are willing to pay. Part of the appeal is the ~150-200 price range. You may be able to stretch it to $250 but at that price you're starting to move into pre-tuned territory.

crassius · Jun 15, 2013

"1. I am replacing the studs and hardware, but what can I do to keep the studs from bending outward when i tighten the nuts down on my bike?
"

if this happens (usually at the rear motor mount) you can cut a small piece (about 1/2 inch wide) of PVC and put it under the collar at the back side of the mount - this way, as it tightens, it will draw the studs in rather than out

2door · Jun 15, 2013

If you're bending studs it has nothing to do with the quality of the hardware but it is an alignment issue as Greg said. Replacing the studs with tougher fasteners doesn't address the problem but might mask it. Find out why the studs are being subjected to the force that is bending them and fix that. Either the frame tubing is too wide or too narrow or the mounts aren't setting properly on them. Replacing them with harder steel will only transfer the stress to the engine case. Break that and you'll be looking at a new lower end.

As for building bikes to sell you'd be well advised to seek the advice of a lawyer and protect yourself from liability claims. If that's even possible. This is what keeps most guys from doing what you plan. Good luck

Tom

Mr. Minecraft · Jun 15, 2013

The studs have been bending out because as I tighten the strap-bracket down over the seat post tube, they bracket bends around the tube. As it bends, it causes the studs to spread apart.

As for the legal side of it, I have yet to figure that out, but it is in my agenda.

crassius · Jun 15, 2013

that's why you'd put the PVC under that strap-bracket to make it bend in rather than out - it'll stop bending when it gets a tight grab onto that post

Mr. Minecraft · Jun 16, 2013

crassius said:
that's why you'd put the PVC under that strap-bracket to make it bend in rather than out - it'll stop bending when it gets a tight grab onto that post

Can you post a pic or drawing of this pcv thing? They way I see it in my head, it will make matters worse.

crassius · Jun 16, 2013

your seat post is over an inch wide - the strap-bracket is even wider - just a half inch piece of PVC under that bracket will lift it off the post a bit so that when tightened it will pinch in until it hits the post which will put a sharper bent in it making it narrower

bairdco · Jun 16, 2013

First of all, good luck. it's tough selling these bikes, and even tougher to turn a profit.

For the tank, a piece of bike chain and some acetone, gas, or similar will clean it out.

for the studs, use m6 hardware. forget about pvc. if you need to make a shim, use steel. an old seapost cut up works great.

As far as the motor, pull the head off, look for metal slivers, then torque it back on and forget about it. offer the same 30 day guaranty as the seller. the more you get into the engine, the less money you'll make and the more time you'll spend.

Make them safe, learn the laws and advise your customers to follow them and explain in writing to ride at their own risk.

Don't build junk.

and keep an eye out for a real job...

Mr. Minecraft · Jun 16, 2013

bairdco said:
First of all, good luck. it's tough selling these bikes, and even tougher to turn a profit.

For the tank, a piece of bike chain and some acetone, gas, or similar will clean it out.

for the studs, use m6 hardware. forget about pvc. if you need to make a shim, use steel. an old seapost cut up works great.

As far as the motor, pull the head off, look for metal slivers, then torque it back on and forget about it. offer the same 30 day guaranty as the seller. the more you get into the engine, the less money you'll make and the more time you'll spend.

Make them safe, learn the laws and advise your customers to follow them and explain in writing to ride at their own risk.

Don't build junk.

and keep an eye out for a real job...

I don't understand why you say its hard to make a profit. Last summer I sold a bike every few weeks, earning ~$150 per bike. I always had multiple people wanting to buy them, so if one fails, I had a backup. Has the market diminished since last year?

mew905 · Jun 16, 2013

I find there's always people wanting to buy a bike but they never go through with it. It depends really on the bike you get. If you can get bikes cheap, then you can turn a profit (used bikes can be had in my area for around $5 to $25). Also depends if you can find people willing to pay $500+ for a new bike and new motor combo. I'll personally never sell a motor kit on its own without upgrading the hardware and bearings, so I install them for $250. If I save up enough to buy them in bulk (10+) or find enough customers, I'll sell em for $200 with the upgraded bearings and hardware. With a bike though that price would jump by $100 if I go with a cheapo Next Challenger, $300-$350 is still a good price. But when you get a decent bike to put it on (like the popular micargi's) then it'd jump by a solid $300-$400+ and thats where the $600 price tag turns people off. At least in my area, but I live in a small town mostly of retired people so I'm not exactly sure what the real market is like.

Mr. Minecraft said:
1. I am replacing the studs and hardware, but what can I do to keep the studs from bending outward when i tighten the nuts down on my bike?

2. Can i replace the studs with long hex bolts (or something similar)?

Here ya go, compiled it for people like you wanting to replace the hardware
http://motorbicycling.com/showthread.php?p=491251#post491251

crassius · Jun 16, 2013

it's OK for a retired guy to pick up a couple bucks, but living on $150 every 3 weeks isn't possible where I live

Mr. Minecraft · Jun 16, 2013

mew905 said:
I find there's always people wanting to buy a bike but they never go through with it. It depends really on the bike you get. If you can get bikes cheap, then you can turn a profit (used bikes can be had in my area for around $5 to $25). Also depends if you can find people willing to pay $500+ for a new bike and new motor combo. I'll personally never sell a motor kit on its own without upgrading the hardware and bearings, so I install them for $250. If I save up enough to buy them in bulk (10+) or find enough customers, I'll sell em for $200 with the upgraded bearings and hardware. With a bike though that price would jump by $100 if I go with a cheapo Next Challenger, $300-$350 is still a good price. But when you get a decent bike to put it on (like the popular micargi's) then it'd jump by a solid $300-$400+ and thats where the $600 price tag turns people off. At least in my area, but I live in a small town mostly of retired people so I'm not exactly sure what the real market is like.

Here ya go, compiled it for people like you wanting to replace the hardware
http://motorbicycling.com/showthread.php?p=491251#post491251

Thanks man, I printed this out and its up in my garage over my workbench.

crassius said:
it's OK for a retired guy to pick up a couple bucks, but living on $150 every 3 weeks isn't possible where I live

I am a 16 year old sitting at home on summer vacation. $150 every few weeks is more than enough for me

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Questions before commercial production

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