Carr Precision DIY kits?

C

Citi-sporter

Active Member
Anyone here tackled one of these kits from Carr in Redmond OR?

Carr Precision's Conversion kit #2

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I have to say this company has more than a little sparked my interest in WMB's, mainly because they offer rather modest engine sizes, and concentrate on the cheaper U.S.A. made weedies like the Green Machine 18~21 cc engines, the Homelite and Ryobi 26 cc two and four stroke engines.

All of their kit designs are sent as plans but they do offer to fabricate some of the lathe turned bits like the pulleys and friction wheels, which makes these kits desirable for those on a limited budget but with some fabricating skill and access to a shop.
 
Looks like a nice set up. In a few hours though one can come up with a similar set up with simple hand tools and Home Depot materials. Search weedeater friction drive on the forum here. Plenty of info.
 
cannonball2 said:
Looks like a nice set up. In a few hours though one can come up with a similar set up with simple hand tools and Home Depot materials. Search weedeater friction drive on the forum here. Plenty of info.
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I have been reading the DIY forum's frictiondrive threads, extensively for a couple years as a lurker.

Actually these designs are not at all like the frequently posted DIY friction setups here. For one thing they are using the weedy engine centered on the 'rack' and use a belt and jackshaft/friction drive. This makes sense since you can customize the drive ratio with different size pulleys. It also introduces a lot of longetivity to these other wise cheap engines.

A lot of the cheapy weedeater engine DIY threads posted on this subforum use the engine off center hung on the rack, and the friction drive mounted direct to the crank, which with the small spacing between the over hung crankshaft of these engines, introduces a side loading that these engines were never designed to handle.

People post a thread about their new friction weedeater drive with a BMX foot peg, it gets a few responses and then disappears down the conveyor belt of new threads.

You know why? Because their engine died soon afterwards from otherwise avoidable main bearing wear and overheating from the cooling shroud missing.
 
Citi-sporter said:
People post a thread about their new friction weedeater drive with a BMX foot peg, it gets a few responses and then disappears down the conveyor belt of new threads.

You know why? Because their engine died soon afterwards from otherwise avoidable main bearing wear and overheating from the cooling shroud missing.
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A Bike peg is much to large for these engines unless you are under 100 lbs.

You need 1" diameter or less. (25cc and less)

There is an aluminum child's peg on ebay that should work.

A larger rider would require the smallest spindle to not lug the motor.
The smallest spindle requires the lowest tire air pressure to develop enough friction to work.
I would think that the "Carr Precision's Conversion kit #2" has belt reduction to allow
a larger friction roller and thus higher tire pressures.

Leaving the shroud on is a good idea. The EPA making these motors too lean
and the carburetors are nonadjustable, on the newer motors.
And with a too large a spindle lugging the motor down, any additional cooling is good.

You can pick these motors out of the trash or $5 yard sales.

If you get 1000 miles, you are blessed because they are so cheap.

Youtube has has a large number of these builds.
 
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No Mat-Man, I'm aware of the need for smaller diameter BMX freestyle pegs on these little engines.

A home mechanic down the street from our shop in '94 was building these engines into friction kits for kids in the neighborhood, and he was using the little 7/8"s BMX aluminum billet foot-pegs you could pick up at at bike shops and variety stores, and mating them with rear rack mounted Homelites and Ryobis.

The problem was the kids riding bikes powered by these engines is after about a couple months use the main bearings developed 1/8" ~3/16" axial wear in them, and soon afterwards the engines died.

These little engines should hold up better. I've got a couple Ryobi weedies that have over 10 years hard yard use and there's no wear in the cranks or rod bearings. And if you don't side load them I'd expect the first thing to wear out would be the chrome bores. Yes they are cheap, but I'm kind of loathe to spend that amount of time making something that gets less than 1000 miles service, if I can make it better and have it last.

I believe that cheap chainsaws would have a better survival rate with direct friction because they have main bearings on either side of the crankshaft, but they present their own challenges for mounting and are far heavier.

Cheers
 
If you could find some old weed eater motors they have a split crank case and bearings on both ends. Pocket bike motors also have split cases and a good size clutch.
I have a KS bike machine motor put out in the 60's it has a Mitchubeshi (how ever it spelled ) motor and is the same size as the pocket bike motor. My KS is clamped to the seat stays, the neat thing about the KS is there is a lever on the side and you can just reach back and lift the engine. Even though it has a clutch on it ........Curt
 
Im not a fan of small engine FDs. I have built one and it worked as expected. I lived not far from Mat Man outside of Athens and the hills in the area all but made the small cc engines impractical. I am an avid fan of FDs though. If I were going to build a practical ride every day FD, I would use a small 4stroke industrial type engine, in frame it and run a large roller via a belt. Its fairly simple and quick to do if you have general fab skills. What you wind up with is a really nice powerful bike that is quiet(if the muffler is left alone) and cruises at a relaxed rpm. The 79cc HF Predator is an excellent candidate and can be had on sale for close to the cost of a throwaway weedeater. I prefer the 98cc Lifan but they are getting hard to find. I realize the engine ccs are illegal in a lot of states and if one wants to be legal then the WE/small chainsaw fills the bill. However I bet there are really very few 49cc China girls out there as well as 20mph ebikes. I have retired my Lifan powered Mongoose with over 8K road miles and never got a second look from any of the locals while riding. I have dealt with Carr Precision in the past, they as well as I had conversions for engines for ultralights/light aircraft. They are good folks and their designs are good, just seems like a lot of work to use what are these days true throw away engines.
 
@ Cannonball.

In my case I'm working with the local Oregon laws that limit un-registered powered bikes/scooters to less than 35 cc's and 25 mph. I suspect that Carr Precision is also working along that legality.

The only throw away part of these little weedies is the attachments and some of the plastic bits. I'm aware of a few folks using Ryobi and Homelite weedie engines as RC model power-plants that have years of flight use on them, considering that aicraft, even model ones run their engines at much higher duty cycles than ground vehicles, this says volumes for the engine's construction.

Locally I have very steep, (but short) hills and summertime small craft advisory strength winds, so having a motor assisted bicycle that can average about 14~20 mph seems like a good compromise. My present 32 cc Echo weedie DIY build is using the same constraints.

Maybe it seems like a limitation to you, but I see it as a freedom. I don't neccessarily need to get somewhere fast, and with proper gearing even 25 cc engines can pull grades. My old Ryobi 825r 4 stroke 26 cc engine is slated for a Carr kit.
 
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I will say the jackshaft fd is much smother and less vibration as opposed to roller on crankshaft. even though I find the roller on crankshaft a more dependable set up. its the same ole problem all us diyers have. harness the power of engine to bike! on the jackshafts I've built ,which I WENT THIS ROUTE TO RETAIN CLUTCH, I have had problems with attaching drive to clutch. Seems when decelerating and engine is braking is when problem occurs. I thought it may have been clutch support, but built a poulan pro 35cc that had commercial style clutch with bearings and all, spent a lot of time using the knowledge gained from others building it. It was good but had about 40-50 miles on it and it puked driveshaft. reworked it and did it again. the clutch housing is in bad shape now. as we speak i'm going direct fd with scissor hands clutch. one other reason I disliked direct fd, was everyone took shroud off and s#^t canned it? I live in Georgia! so I took Ryobi 31cc shroud and sawed it flush with flywheel! I will post some pics. some guy spent a lot of time designing that COOLING shroud for us to just disregard it!
 

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Yeah I have to agree, What I've noticed is that the home market, cheaper weedy engines tend to have cooling fans and shrouds that are by most measures, just adequate.

While the Swedish, German and Japanese weedies tend to have really robust cooling systems with lots of well controlled airflow. If you have an old working Homelite or Ryobi weedy fire it up and run the engine while holding your hand over the cooling duct exit, I 'll bet dollars to donuts the better quality engines blow a larger volume of air.

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These better engines are also the ones that support the crankshaft on either side and use heavier internal design and construction.

I suspect that the better engines would last another 30 years with proper gas-oil ratios and maintenance. They may not be a powerhouses, but they weren't really designed for WOT use as much as constant mid throttle loading.
 
I am an avid RC flier and have converted a bunch of WE engines. I was also in the small engine trade for 20yerars so I had free pickings of cast off equipment. The old Ryan 31cc was a bullet proof engine single ended crank and all. I believe it was designed by OMC. It evolved into the Ryobi and was still a good unit. You couldnt kill an old Homey 26/30cc. Not to mention the Echos. The list goes on. The engines these days are way less quality imports for the most part. If I had to build a small cc FD I think I would look for used Stihl 4mix, quite a power house and very reliable. Chain saw engines offer the best performance/cc and are also very durable if scrounged from older saws. The last product school I attended listed the life of the particular branded engine at around 40hrs, a long time trimming your yard. However only 800mi@ 20mph.
 
I am not a fan of these small cc engines. I would prefer at less 46cc saws which are a little heavy (around 10 lb) but they do whatever i want to do. There is a detailed report, published in a caldera. You should take it as a reference.
 
I still want to see somebody using the disc cutter engine and transmission, it looks like a straightforward conversion to FD, using motors that are required to be robust to sell.

Like this

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Makita 76cc 4-Stroke Power Cutter
4.1 HP @ 9,350 RPM

This is the one I like, only $1200:
 

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Why bother with FD? Even a tiny engine is better off with positive drive.

I put a 1E44F-5 string trimmer engine on my 29'er with chain drive
http://motorbicycling.com/showthread.php?t=57161

Sure, it is 50cc's - but a 33cc sticker will fix that right up. Runs like a champ. A 2hp champ. With an intact cooling system.

Carr is full of it about the clutches. The engine manufacturer provided a clutch that is up to the full output of the engine. Just gear it properly. I beat on my 29'er at the Grange to break it - now I ride it WOT on the street. Clutch is doing just fine.

There are a couple of transmission choices out there to fit this engine, and with a 5:1 reduction you are one sprocket from done.
 
Why bother with FD? Even a tiny engine is better off with positive drive.
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No doubt that 29'er is sweet. All you need is a 2-horse 50cc motor and a "how much money?" CVT gear reduction to run it "positive drive".

I agree with the hazard of side load on the shaft (crank) bearing with trimmer motors (especially the single-supported ones). I disagree with the obsession with retaining the factory shroud. Shrouds are great on a weed-eater. It operates practically motionless, and your arm is protected.

Everyone with a bare motor (like a ChinaGirl or moped or motorcycle) needs to put a homemade shroud around it immediately or else it will blow up.

Maybe I will start a business for chinagirl shrouds. Anybody wanna buy one?
 
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