Resurrecting Old Yeller
- Thread starter cyclejunkie
- Start date
- Tags resurrecting yeller
mikuni/clone carb's are pretty forgiving for mild to radical. nice thing about them they have adjustments for lowend ,mid-range and top end.
what every you end up with for your engine build a mikuni/clone will work good.
some of the other problems that i see you could have is the bushing motor and i'm not a big fan on revving a bushing motor up to 8000+ with the gearing you have. pto bearing cover would help little. i believe you have a 17tt clutch with a 1800 engagement? kind of sounds like a autobahn gear. that would take a very long distance to rev it up to 8000+ and some crazy top end speed for that little bike and at that point you would think that would be hard on the bushing bearings. i have had good luck with short high rev's on bushing engines. but thats it. never tried long distance with them. also don't think the factory 3 rings setup(thick rings) are a good design to rev a aluminum bore at 8000+ long distance. person can get a motor like that to rev to 8000+ but i think it maybe a short lived engine? i know david has had good luck with his hs-50 revving very high. but that too his something he just does in short distances(100ft +) and then let's up on it. doesn't try to go for 10 blocks at 7000+
i do enjoy watching you build and it's always cool to see a guy build a minibike with a flathead on it......:thumbsup:
what every you end up with for your engine build a mikuni/clone will work good.
some of the other problems that i see you could have is the bushing motor and i'm not a big fan on revving a bushing motor up to 8000+ with the gearing you have. pto bearing cover would help little. i believe you have a 17tt clutch with a 1800 engagement? kind of sounds like a autobahn gear. that would take a very long distance to rev it up to 8000+ and some crazy top end speed for that little bike and at that point you would think that would be hard on the bushing bearings. i have had good luck with short high rev's on bushing engines. but thats it. never tried long distance with them. also don't think the factory 3 rings setup(thick rings) are a good design to rev a aluminum bore at 8000+ long distance. person can get a motor like that to rev to 8000+ but i think it maybe a short lived engine? i know david has had good luck with his hs-50 revving very high. but that too his something he just does in short distances(100ft +) and then let's up on it. doesn't try to go for 10 blocks at 7000+
i do enjoy watching you build and it's always cool to see a guy build a minibike with a flathead on it......:thumbsup:
Thanks Delray for the info, I knew that the stock rod assembly and such would be limiting from the research I did. The stock rod is supposed to be good to around 5400, witch is why I was thinking about limiting it to 5. What your saying about the bushing set up makes sense, I had wondered about that. Considering a mikuni clone I will be doing. Is there a brand for that or can I just search some after market carbs? Plans were to hook up a tach as well.
you can just do a search for 22mm mikuni/clone carb ebay. you should come up with this type of carb.
https://www.ebay.com/itm/Mikuni-Car...42&rk=1&rkt=1&&_trksid=p2045573.c100642.m3226
you might be able to find it cheaper? sure someone can chim in and let you know if so.
if you are using the original stock rod from that motor without the governor? i would not trust it above 4000 rpm's
the newer rods that come in the late model small blocks-5hp flatheads and ohh-motors seam to be a little better quality rod. if i had to pick the two worst rods in a tecumseh. first it would be a hs-4hp and second a 7hp motor.
i have a mild built ohh-motor with the rod beam cleanup/polish and thats been running for two years without the governor. little engine pulls good up to 4700 rpm's with a newer style stock steel cam with 15# pound springs and aftermarket valve retainers/keepers and 30 degrees advance (coil unit)
this might be little better setup for a bushing motor. i also still recommend buying a billet rod and maybe looking for a bearing pto cover......:thumbsup:
https://www.ebay.com/itm/Mikuni-Car...42&rk=1&rkt=1&&_trksid=p2045573.c100642.m3226
you might be able to find it cheaper? sure someone can chim in and let you know if so.
if you are using the original stock rod from that motor without the governor? i would not trust it above 4000 rpm's
the newer rods that come in the late model small blocks-5hp flatheads and ohh-motors seam to be a little better quality rod. if i had to pick the two worst rods in a tecumseh. first it would be a hs-4hp and second a 7hp motor.
i have a mild built ohh-motor with the rod beam cleanup/polish and thats been running for two years without the governor. little engine pulls good up to 4700 rpm's with a newer style stock steel cam with 15# pound springs and aftermarket valve retainers/keepers and 30 degrees advance (coil unit)
this might be little better setup for a bushing motor. i also still recommend buying a billet rod and maybe looking for a bearing pto cover......:thumbsup:
Yes, you can find them cheaper. Here is a cheaper carb.
Danford1
https://www.ebay.com/itm/CARBURETOR...ash=item212c42175f:g:z1IAAOSw4X5Zyo0t&vxp=mtr
Danford1
https://www.ebay.com/itm/CARBURETOR...ash=item212c42175f:g:z1IAAOSw4X5Zyo0t&vxp=mtr
Sorry guys for the delay in the program, but its been a heck of a winter, ( I drive a fuel delivery truck) shoveling snow , and working in my buddies shop ( who passed away back in June ) , but here we are.
Here are a couple of pics in the process.
The mount I had fab to get the clutch and rear sprocket to line up.
Had to make the adapter between throttle cable and mount.
Here we are with the throttle hook up I engineered.
Here are a couple of pics in the process.
The mount I had fab to get the clutch and rear sprocket to line up.
Had to make the adapter between throttle cable and mount.
Here we are with the throttle hook up I engineered.
I decided last Saturday it was time to see if this ol girl was going to run. First I wanted to see if she had any spark. ( I had adjusted the points but not the coil) She had a nice strong blue spark and I started to get excited. I took her down of the bench, put some gas in the tank and turned it on. Next I gritted my teeth and yanked the cord. (from what some guys said I expected to break an arm, but wasn't that bad) Pulled a few times then she popped. Gingerly cracked the throttle. Wasn't sure what to expect when it fired. She fired then stalled cause I let off the throttle being nervous. Yanked her again and man does she sound awesome, and the throttle response is great. The street outside (on private grounds) was clear enough I decided to give a try. Coasted down the street ( street goes down hill toward a lake) because I didn't have the brakes hooked up yet. Fired her up cranked her up the hill, she took off decent considering how she is geared.
She just started winding up. I shut her down when I got back to shop. This thing is going to run like a bandit .
She just started winding up. I shut her down when I got back to shop. This thing is going to run like a bandit .
cool :thumbsup: I just tried a modified H50-70 carb on a HS40 I just rebuilt for someone. far as current replacement carbs go they have the same detent for the choke lever that most of the mini bike specific HS40's and 50's used so I converted the throttle and choke levers over. the larger drilled high speed jet they come with seemed to be too much for it so I threw a smaller one in from a small frame carb. It sounds nasty (good nasty :thumbsup
and revs up faster on the bench but is feeling a little finicky for stock engine so I am back to cleaning up an original carb body for that build. But I think it will work on something with a little port work, etc. moreso on a larger bore like the HS50's. keep us updated how it goes when you get it better dialed in and some brakes on it :thumbsup:
and revs up faster on the bench but is feeling a little finicky for stock engine so I am back to cleaning up an original carb body for that build. But I think it will work on something with a little port work, etc. moreso on a larger bore like the HS50's. keep us updated how it goes when you get it better dialed in and some brakes on it :thumbsup: