New Tecumseh HS40 carb(s)

cfh

Well-Known Member
#64
Have a Rupp Hustler with an original HS40 motor. It runs really nice with the new (china) carb, but wanted a little more out of it. So i installed the 16mm china carb. Installation not quite as clean as the other bikes, because of the way the exhaust bends. But overall worked out well. Performance much better, more top end and smoother thru the entire RPM range. One of the problems with the Tecumseh stock carb system is it's very reactive to changes in temperature (wants the high speed jet to be slightly adjusted to avoid dead spots.) The 16mm carb does not have this issue.

 
#65
The ideal bore size for the hs50 would be a 22mm carb if it’s jetted correctly. Remember the big block h50 which is also 5hp just like the hs50 used the mb22a dellorto carburetor as a performance upgrade, they also used the mb22a on the rupp ss-5 hs50 as a performance upgrade. The mb22a used a 50 idle jet and a 105 main jet, so these might be a good starting point for a 22mm carb. I’ve also heard of people successfully using an mb24a on the h50. The mb24a is a lot cheaper to get than the mb22a.
 
#66
The tillotson carburetor like used on the performance powersports h50 would also be a nice carb to try. You can get the tillotson copy for cheap.
 

delray

Well-Known Member
#67
The ideal bore size for the hs50 would be a 22mm carb if it’s jetted correctly. Remember the big block h50 which is also 5hp just like the hs50 used the mb22a dellorto carburetor as a performance upgrade, they also used the mb22a on the rupp ss-5 hs50 as a performance upgrade. The mb22a used a 50 idle jet and a 105 main jet, so these might be a good starting point for a 22mm carb. I’ve also heard of people successfully using an mb24a on the h50. The mb24a is a lot cheaper to get than the mb22a.
cfh
Have a Rupp Hustler with an original HS40 motor. It runs really nice with the new (china) carb, but wanted a little more out of it. So i installed the 16mm china carb. Installation not quite as clean as the other bikes, because of the way the exhaust bends. But overall worked out well. Performance much better, more top end and smoother thru the entire RPM range. One of the problems with the Tecumseh stock carb system is it's very reactive to changes in temperature (wants the high speed jet to be slightly adjusted to avoid dead spots.) The 16mm carb does not have this issue.
I know a hs-40 with a 19mm dellorto will run very good with a ohh-steel cam with compression relief,porting,timing advance,header,billet rod,aluminum flywheel(factory points style) engine will pull easily up to 4500 rpm's.


AjF
mb22a on the rupp ss-5 hs50 as a performance upgrade
where did you find this information that rupp made this a option. do you have a rupp brochure or something with this info. I like to see this too if so.....:thumbsup:

AjF
Ajf
The tillotson carburetor like used on the performance powersports h50
I have HL 365B tilly that was for a Tecumseh motorsport engine and that has a .750 bore making it only a 19mm bore. not say that a 22 won't work. just showing what Tecumseh motorsports ran this on some of it's racing stuff. also they use a bowl carb design that came from a 8-10hp big block and that too looks to have only a .750 bore. i'm still with you on a 22mm working with the right up grades...:thumbsup:
 
#68
Rupp used the mb22a as an upgrade on the 68-69 h50 bikes, they also had a performance exhaust. They also used it again as an upgrade on the ss-5 and it was originally going to be factory but ended up an option. There were no internal upgrades from rupp directly. I have some stuff on my phone from the rupp parts manual. I have more literature but I need to find. It is well known that rupp used the mb22a if you do a search there is lots of discussion on it 0D8648D4-912E-4210-BBF8-B4EACFFD3A94.jpeg 2548313A-EE72-4004-9632-741E141E7511.jpeg 3C6F1E0F-E759-45D4-B6BF-F31525C8BAE6.jpeg
 

delray

Well-Known Member
#69
yes Ajf I am aware of the 22 up grades on the TT500's ….:thumbsup: I personally never seen any info printed from rupp using the 22 as a up grade on the ss-5 bike. that would be nice to see if you have any info on the ss-5 bike using this...:thumbsup:
 
#70
yes Ajf I am aware of the 22 up grades on the TT500's ….:thumbsup: I personally never seen any info printed from rupp using the 22 as a up grade on the ss-5 bike. that would be nice to see if you have any info on the ss-5 bike using this...:thumbsup:
[MENTION=26537]Rupp 72[/MENTION] had posted the dealer spec sheet for the ss5 awhile back but the photo is now missing from the thread. I have one I need to locate but maybe he will see this and repost his photo.
 

cfh

Well-Known Member
#71
I have a dellorto ub22 on an HS50 tecumseh motor for an mtd. I don’t know what the jetting is though, it’s running what came with it. But it works very well. I don’t really notice a huge difference between it and the Ua19. I do know that the ub22 chews a lot more gas though, it’s hangry.
 

Rupp 72

Active Member
#72
Rupp used the mb22a as an upgrade on the 68-69 h50 bikes, they also had a performance exhaust. They also used it again as an upgrade on the ss-5 and it was originally going to be factory but ended up an option. There were no internal upgrades from rupp directly. I have some stuff on my phone from the rupp parts manual. I have more literature but I need to find. It is well known that rupp used the mb22a if you do a search there is lots of discussion on it View attachment 107907 View attachment 107908 View attachment 107909
I truly don't think Rupp ever used the MB22A on the SS-5, not even as an option. I have tried to install my MB22A onto my SS-5 and it doesn't fit. The carb hits the bottom of the gas tank. I think the intention was to use it on the SS-5 but i don't believe rupp ever actually did. During the time this bike was being developed was also during the same time minibikes were being phased out and rupp was going bankrupt. I have a feeling this performance upgrade was comprimized just to get the bike in production and on the market in an effort to stay afloat. I have seen many SS-5 bikes and none that I have seen have had a MB22A on them. There is the only picture I found on the internet that does have a MB22A on it but it appears to have a special intake that drops the carb down so it fits. I am not certain this is the case, it potentially could have been a option, but I haven't ever seen prof of that.



yes Ajf I am aware of the 22 up grades on the TT500's ….:thumbsup: I personally never seen any info printed from rupp using the 22 as a up grade on the ss-5 bike. that would be nice to see if you have any info on the ss-5 bike using this...:thumbsup:
[MENTION=26537]Rupp 72[/MENTION] had posted the dealer spec sheet for the ss5 awhile back but the photo is now missing from the thread. I have one I need to locate but maybe he will see this and repost his photo.
Notice the note at the bottom of the page! *** "At time of publication engine specifications were not firm and may be different on production units" ***

So yes, I think the intention was to use the high performance MB22A carb, weather or not they did at all, still can't be certain?:shrug:

 

delray

Well-Known Member
#73
thanks nate for posting that info...:thumbsup:

was this maybe the other bike you seen with the carb on it. note too it is mounted different from the brochure. I think this was a custom mod on this bike.
that bike looks bad ass. I would have a hay day with that hs-50 motor. make it go like you where riding a 125+ dirt bike......:scooter:
 

cfh

Well-Known Member
#74
Got some the new toys set up and ready for installation.
a Dellorto ua18s and the Dellorto/Lambretta 19mm are ready
for motors. i have to finish up some bikes to put them on
though...





Also regarding the Dellorto ub22s, this picture was posted earlier, but here it is on my MTD.



 

cfh

Well-Known Member
#77
on the throttle cable... that's why i generally put in those aluminum block spacers, to get the cable away form the exhaust. but on the Dellorto ub22 the cable isn't near the exhaust. it looks like it is, but it really is not.
 

delray

Well-Known Member
#78
couple things that look interesting on that ss-5 brochure. bike is a lighted coil/headlight setup. I never seen a lighted coil model before and the other thing was the horse power rating. they have that hs-50 rate at 6hp. got to be rated with the header and dellorto carb?
 

Rupp 72

Active Member
#79
thanks nate for posting that info...:thumbsup:

was this maybe the other bike you seen with the carb on it. note too it is mounted different from the brochure. I think this was a custom mod on this bike.
that bike looks bad ass. I would have a hay day with that hs-50 motor. make it go like you where riding a 125+ dirt bike......:scooter:

This bike has a UA19S carb. Not an MB22a carb on it which is why it fits. Two totally different style carburetors.
 

delray

Well-Known Member
#80
yes nate, the original rupp 19mm dellorto can mount side ways because of the bowl mount they use. will a 19mm bowl still work on a 22mm.
 
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