Cagllari 47cc Engines For Gas Bike Use?
- Thread starter dbledsoe
- Start date
maniac57
Old, Fat, and still faster than you
As long as you know what you're going to have to fix and why, no reason you can't fly.
When they WERE running, the Cag's had very good power, especially with the right pipe and carb. Needs to rev though, so address the jug floating and you'll do fine.
And buy or fab a better, more durable reed.
Reeds were the single biggest problem area I had on the Cags I messed with. All were crap even brand new, so the gouged up high mile piles I saw were a huge pita to figure out. I hear good things about a Mallossi reed, but you'd have to google that
Don't think for a second I don't look at stuff like this and wonder....
Oh yes! I hear you on that! Exotic motors get the juices flowing, which is mostly why I want to try my hand at it. It's a side project, not something I would build to sell. It will be for me (only) so if it blows up, no big deal... but I will try to build it right so it doesn't blow up or pull itself apart.
I have a stock Cag engine with 3/1 reduction trans and a pipe. It will also get carbon fiber reeds and a Delorto SHA 15.15 carb. Other than that it will remain stock. I just need to find a suitable frame to start the build on. The hot rod stage Cag will be built separately starting with a new set of crank cases, a full circle crank assembly, and hi comp cylinder/head parts. Once the basically stock Cag motor build proves out I will then try swapping in the hot rod Cag motor.
This is going to be a long term project. I have five other builds in progress as I write this. Three are based on Skyhawk GT2A frames and China Girl engines, but all three have specifically different versions of the China Girl engine. The other two are built on Worksman bikes, one a Worksman INB with another China Girl engine version with a lot of Sportsman Flyer parts, and the one that will be mine is based on the Worksman Sportsman Flyer bike and has a 79cc four stroke engine installed. All are being built to sell via my newly formed business; Boise Gas Bikes... but mostly the Sportsman Flyer four stroke build will be for me.
All that as it may, I have a soft spot for pipy high RPM narrow power band two strokes. I cut my performance teeth with a 1971 vintage Suzuki TS50 rotary valve intake 50cc motorcycle as my transportation while going to college in Los Angeles. I ported, modded it, bought the Suzuki factory expansion chamber, and set it up to run on straight methonal. Power band came on at 8k rpm and ended at 11k. It is difficult to convey but the three thousand RPM width power band lasted maybe 1 second, probably closer to 1/2 Second. That high strung Suzuki 50cc would blow so many Honda factory bikes away, all the way up to 125, and even most factory stock 160's. It was obnoxiously loud (not sonething that bothered me back then but no doubt it did my older neighbors).
So I welcome a pipy high strung two stroke motor. Maybe not ideal but darn sure a lot of fun.
Don
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cannonball2
Well-Known Member
Be sure you thread what you are doing. I think all of us like the Cag. Would be nice to see a hi-pro build hang together.
I have run the SHA/clone carb on several engines and found it never to really be totally tuned to my liking. Maybe on a all top end bike it would work well. Another choice might be the Walbro clone carbs. They can be had with a 15mm bore fairly cheap and most have a mixture screw.
Keeping the overall ratio low is important to allow the motor to band. Thought it will pull(stock anyway) off band, if geared properly it will hit hard from the get go and keep on pulling. A geared bike is an excellent home for a Cag. My 6spd shifter started with a ratio of over 30:1 as I remember and the spacing on the gears was nearly perfect to keep it banded. The light torque loading of the engine is pretty easy on the shifter mechanics. However I never speed shifted, but backed of a bit.
Keep us posted!
I have run the SHA/clone carb on several engines and found it never to really be totally tuned to my liking. Maybe on a all top end bike it would work well. Another choice might be the Walbro clone carbs. They can be had with a 15mm bore fairly cheap and most have a mixture screw.
Keeping the overall ratio low is important to allow the motor to band. Thought it will pull(stock anyway) off band, if geared properly it will hit hard from the get go and keep on pulling. A geared bike is an excellent home for a Cag. My 6spd shifter started with a ratio of over 30:1 as I remember and the spacing on the gears was nearly perfect to keep it banded. The light torque loading of the engine is pretty easy on the shifter mechanics. However I never speed shifted, but backed of a bit.
Keep us posted!
16v4nrbrgr
Active Member
It's way cheaper to buy an assembled "stage 3" engine and rebuild it than building one from parts. Since these are Chinese, there are multiple factories with different parts dimensions, so getting an assembled and running engine is a good way to ensure all the parts are from the same factory and will work. You should be able to build one from parts, but be careful with all the clearances.
A note about the reed valves, the stock metal ones will fatigue over time and cup, eventually not sealing the intake properly. That also have a tendency to fatigue and break off and munch motors. The cheap cf reeds work well and can be limited in their bending travel by a cut down metal reed. The limiter makes the reed last longer and can be used to tune the spring rate of the reed as well.
A note about the reed valves, the stock metal ones will fatigue over time and cup, eventually not sealing the intake properly. That also have a tendency to fatigue and break off and munch motors. The cheap cf reeds work well and can be limited in their bending travel by a cut down metal reed. The limiter makes the reed last longer and can be used to tune the spring rate of the reed as well.
Today I received the new Cag stripped crankcase, along with the crank bearings and crank seals I ordered. Looking over the crankcase halves I see the the case cylinder stud holes are not blind holes, rather they are through threaded holes and it appears possible to open the holes up and rethread to accept 1/4-20 or 1/4-28 grade 8 studs and put modified (turned down) nuts on the back side of the studs to prevent them pulling out the case threads rather than Helicoil the case. Still, Helicoil is a viable option. Will have to make a decision on how I want to proceed but it is nice to have options.
Don
Don
16v4,
Thank you for the link to your thread!
Sadly I figured out what you already knew, but only after ordering the big bore Cag kit I originally intended as a down the road modification/add on to the stock Cag engine I bought. That was before I knew the short comings of trying to do a Stage X kit install on a stock engine block. I am now committed so will proceed with a parts build of a second engine. I have, and will continue to, buy all the Stage X stuff as well as the new baseline lower engine parts from the same place in hope I can avoid dimensional cross contamination of parts.
The CF reeds I bought are anything but cheap.
Don
An interesting plan with the nut inside the case. They already make the nut:
http://holokromefastenal.thomasnet-navigator.com/viewitems/allen-nuts/allen-nuts-heat-treated-steel?
.
FFV8,
Thanks a ton for that link. That's exactly what I need, along with some new studs.
Contrary to what I previously said about the Helicoil option, well upon closer examination of the bare crankcase Helicoil is not an option. The boss inside the crankcase that the studs screw in to does not have enough material surrounding to accept a Helicoil. Trying to open the threads big enough to accept the Helicoil would blow the boss out. So the Allen nuts seem the best option.
Thanks to FFV8 for the tip re: Allen nuts. The link provided was for US threads. Since, if I have to use the Allen nut approach I thought it might be best to look for metric Allen nuts so did a duck duck go search and came up with this outfit, http://www.ballerbolts.com/index.html. They offer the Allen nut in M6-1 size so I ordered 4 of those. Then I went searching for M6-1 studs of 100mm (4") length and ended up at McMaster-Carr. They offer a 1 meter length of M6-1 threaded rod Class 10.9 so ordered that too and will make my own studs to the exact length I need. Staying metric I don't have to rethread the crankcase and am getting high strength stuff. May have to do a wee bit of Dremel work on the crankcase to clear the Allen nuts. Hopefully it will not be overly extensive.
Once I get to the point I think the Cag Stage X build is feasible i.e., install the class 10.9 studs in the case with Allen nuts to keep the studs from pulling out of the crankcase threads then I'll start looking for a bike frame to fab up and mount the basically stock Cag engine into. But then again, I do have my son's old 90's vintage Specialized MTB doing nothing but taking up space in the garage. Hmmmmm... might work as a suitable candidate after a complete tear down, media blast, powder coat of the frame, and new bearings and races.
Once I get to the point I think the Cag Stage X build is feasible i.e., install the class 10.9 studs in the case with Allen nuts to keep the studs from pulling out of the crankcase threads then I'll start looking for a bike frame to fab up and mount the basically stock Cag engine into. But then again, I do have my son's old 90's vintage Specialized MTB doing nothing but taking up space in the garage. Hmmmmm... might work as a suitable candidate after a complete tear down, media blast, powder coat of the frame, and new bearings and races.
cannonball2
Well-Known Member
Realizing you have laid the ground work for an air cooled Cag adventure I just thought I would throw this out there for consideration. Seems like a cheaper way to a true hi pro engine. This one doesn't have the specs listed but I seem to remember 13k rpm and some pretty healthy ultimate HP. Small radiators can be had used. I bought a KX65 version for a project I have waiting for $20. Just a thought.
http://www.ebay.com/itm/39CC-Liquid...ash=item3f5822260a:g:tUEAAOSwu4BVsBBY&vxp=mtr
http://www.ebay.com/itm/39CC-Liquid...ash=item3f5822260a:g:tUEAAOSwu4BVsBBY&vxp=mtr
As you note, I am already committed to the Cag i.e., too much invested to change course now, not to mention the liquid cooled 39cc engine seems to suffer reliability problems too. China 2 stroke motors seem to share reliability problems.
16v4nrbrgr
Active Member
I like the idea of using those Allen nuts. I had to lathe down the OD of M6 jetnuts to make them fit inside the case. These motors have a sound internal design but make more combustion pressure than the cases can take at the head bolt holes, and they vibrate which causes it to walk around too. Great light little motors though, and if you don't try to bog them with tall gearing it should last a while before blowing up. Im hoping mine provides a lot of riding time, I've been saving the hours on mine and riding carefully because it took a lot of work getting it to hold together.
16v,
The Cag has a lot of potential if one examines its weak spots when building a very high compression motor. They are fairly easy to spot, the cylinder studs to case mating being, arguably, the major weak spot. But that can be fixed with nuts to capture the studs inside the case. As I see it, the Allen nuts will prevent stud pull out but the Allen nuts will have to be torqued up tight against the engine case stud bosses to best retain the studs where they should be. And suitable strength studs are a must to prevent stretching when cinching (torquing) the head with out stripping the cylinder head nut/stud threads.
I am in receipt of a 1 meter length of class 10.9 (better than USA grade 8) M6-1 threaded rod that I will make my cylinder studs from. I am still waiting on receipt of the Allen nuts.
Another area one might consider a weakness in the Cag is the four bolts that hold the crankcase haves together. They are threaded into the aluminum case on one side. I consider that a potential weak point. Then again it maybe it really shouldn't be since what we are actually aiming for is an increase cylinder head compression with the hot rod top end whereas the crankcase compression should remain about the same, which the stock Cag crankcase seems able to contain. But if one wants to be on the safe side i.e., overbuild the cases, a wee bit of opening up the threaded side of the case with hand drill to accept Allen nuts should do the trick. Do that and we can torque the crankcase half bolts to the point they will snap before they will ever pull out.
Keep in mind, I have never built a Cag engine. This is my first. But I have built a boat load of engines of varying types. Been doing so for over 50 years.
Some engines are designed right the first time around if kept within their original design specs. Others easily lend themselves to modification to a point never intended in the original design, the small block Chevy engine comes to mind. Trying to improve some engines simply pushes the original design beyond its limits. I think that is where the Cag engine fits in. It is easily modified with bolt on parts that ignore the intent/limitations of the base design... but it can be shored up... and that's where we come in.
16v4nrbrgr
Active Member
I'll be paying attention to how your motor strengthening works out, since I would like to someday make a higher comp ported motor based on the relatively affordable stage 3 motor. I think that a base model cylinder cag engine rebuilt with the hardware upgrades would probably have longevity on par with the utility 2 strokes for pocket bikes, which are quite a reliable engine. The reeds on the cag fill out the powerband better than the piston ported ones, so you can cruise with lower clutch pickup rpm. I feel like the cag is a bit more refined of an engine than the Mitsubishi clone, it really performs well for the price, so reliability is really the only obstacle with its use. Some have claimed to build cag motors that make around 10 hp, which is quite incredible considering the engine only weighs 7 lbs!
I will keep you posted re: my Cag motor build.
I agree the Cag is a more refined engine than the typical China Girl piston port engine, although neither are made of very good base materials. Still, I think the Cag can be strengthened to be the better HP output engine. I can see how the Cag could be a 10 hp engine, with a lot of work... and some prayers that it doesn't blow up.
As usual, one step forward then two steps back.
I received the class 10.9 6m .1 threaded rod, 1 meter of it. That's good. What I cannot get is the 6m .1 Allen nuts I ordered from ballerbolts.com. Have emailed them twice with no response. Will try calling come Monday but I don't hold out much hope. They are a very high end nuts and bolts supplier to folks who build exotic Porsches. I doubt my $18 order for four nuts gets their attention.
My backup plan was to order 3ft of 1/4-20 and 3ft of 1/4-28 grade 8 threaded rod to make the studs from, along with suitable quantity of 1/4-20 and 1/4-28 Allen nuts from McMaster-Carr, which is on the way to me. I had hoped to stick with the factory 6mm studs but that is proving not possible via American suppliers (great difficulty finding metric fasteners in the USA, and I don't know why when so much is changing here to metric?). I didn't really want to re-tap the case threads for USA size but guess I will have to if I hope to get this engine built. I want to have on hand both 1/4-20 and 1/4-28 to determine which is the best change from 6m-.1.
More info when I get it.
Don
I received the class 10.9 6m .1 threaded rod, 1 meter of it. That's good. What I cannot get is the 6m .1 Allen nuts I ordered from ballerbolts.com. Have emailed them twice with no response. Will try calling come Monday but I don't hold out much hope. They are a very high end nuts and bolts supplier to folks who build exotic Porsches. I doubt my $18 order for four nuts gets their attention.
My backup plan was to order 3ft of 1/4-20 and 3ft of 1/4-28 grade 8 threaded rod to make the studs from, along with suitable quantity of 1/4-20 and 1/4-28 Allen nuts from McMaster-Carr, which is on the way to me. I had hoped to stick with the factory 6mm studs but that is proving not possible via American suppliers (great difficulty finding metric fasteners in the USA, and I don't know why when so much is changing here to metric?). I didn't really want to re-tap the case threads for USA size but guess I will have to if I hope to get this engine built. I want to have on hand both 1/4-20 and 1/4-28 to determine which is the best change from 6m-.1.
More info when I get it.
Don
The "CAG" is a re-purposed agricultural engine. The remains of a cooling system & that plug boot are a big clue.
The brush cutter / string trimmer concept is a Japanese one. The engine on the end of a stick allows the cutting head to be used under water - think rice paddy. In the beginning they used a backpack mounted engine with a big flex shaft.
The "CAG" is an old Fuji design. The float carb worked on a backpack just fine. That is why there is no provision for a crankcase pulse / diaphragm carb.
Like all things once made in Japan, they wind up in China being produced decades after they are obsolete in Japan
Recognize that cooling shroud? Plug cap?
The old Fuji design was a solid one. Idle was 3,000 rpm, max speed 9,000 rpm.
Pulled cylinder base threads are probably related to poor material quality rather than the original design.
Re-threading to 1/4-28 is probably a good fix, the cross section on threaded rod is better than the M6 stuff.
The brush cutter / string trimmer concept is a Japanese one. The engine on the end of a stick allows the cutting head to be used under water - think rice paddy. In the beginning they used a backpack mounted engine with a big flex shaft.
The "CAG" is an old Fuji design. The float carb worked on a backpack just fine. That is why there is no provision for a crankcase pulse / diaphragm carb.
Like all things once made in Japan, they wind up in China being produced decades after they are obsolete in Japan
Recognize that cooling shroud? Plug cap?
The old Fuji design was a solid one. Idle was 3,000 rpm, max speed 9,000 rpm.
Pulled cylinder base threads are probably related to poor material quality rather than the original design.
Re-threading to 1/4-28 is probably a good fix, the cross section on threaded rod is better than the M6 stuff.
FFV8,
Thank you for that info. I think you are correct as to the origin of the Cagllari engine. The Chinese steal from others and rebrand with euro sounding names. They have been doing it for years. But then again, they often steal the right stuff and repurpose it. There isn't much they won't steal and sell as their own. I have that from a source in the PRC.
Thank you for that info. I think you are correct as to the origin of the Cagllari engine. The Chinese steal from others and rebrand with euro sounding names. They have been doing it for years. But then again, they often steal the right stuff and repurpose it. There isn't much they won't steal and sell as their own. I have that from a source in the PRC.