Tecumseh, Dellorto, slide carbs, Black Widow

#22
I know your just playing around with the two different carbs and all. looking to see how it improves the performance. like you said early there was a small improvement,but that was it. you will never see much more either unless you do the whole package deal. better cam,advance timing,gearing,good header on the bike....etc.....that snowblower intake is terrible. can't get anymore restricted then that. mm carbs are made to go and there is nothing really there to help it go....:scooter:
main thing your having fun with it and it's aways fun to play around on this stuff......:thumbsup:
So in your opinion delray,

Would a 20mm slide carb be enough for a built hs50?
I see 20mm carb listed for 70cc engine, hs50 is almost 200cc. Then porting cam springs etc
Like is it ok for stock hs50 and built hs50? Or more so the stock hs50?
Would a 22mm carb be better for a built motor?

Just curious thanks
 
#23
The exhaust on my "black widow" (jury still out if it's a real BW!) is a bolt on. But i suspect there is a baffle. i haven't taken it off (yet) to check. i'm just happy it's running, and running well with the Dellorto!

are you saying having a straight pipe gives a 20% increase in performance over a baffled pipe? i find that pretty hard to believe there would be that much difference...
It is a 20 percent increase in exhaust flow, not horsepower. Although this increased flow will equate to more horsepower, the actual amount of increase can only be measured by a dynometer.
 

cfh

Well-Known Member
#24
I installed the $22 slide carb on my Fox thunderbolt 160 yesterday, using the 1" spacer. For my exhaust, it needed just a bit more length, so i actually used two spacers (the second spacer was a tecumseh product i bought somewhere.) Note this is a 20 degree slant engine application, and this bike is using a Blackwidow Motorsport tecumseh angled intake manifold. Obviously i removed the original Tecumseh carb from the manifold.

all i can say is it works great. It is easily as nice a performance addition as the Dellorto was on the Black widow. Much more responsive and better high end. If i can make the spacers more easily, this would be a great addition to any 5hp Tecumseh (haven't tried it on a 4hp yet.)

Total cost....
carb with air filter $22 (from ebay, included shipping.)
Throttle with cable $11 (from amazon).
Spacer block... cost unknown because its home made.

 
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delray

Well-Known Member
#25
massacre
So in your opinion delray,

Would a 20mm slide carb be enough for a built hs50?
I see 20mm carb listed for 70cc engine, hs50 is almost 200cc. Then porting cam springs etc
Like is it ok for stock hs50 and built hs50? Or more so the stock hs50?
Would a 22mm carb be better for a built motor?

Just curious thanks
if your talking about a built hs-50, then I would say a 22mm would be the way to go. good example of a hs-50 built.
david wulf hs-50 ported,hot coil, 255 cam...etc.. and he has run a 22mm carb and even a tilly...:scooter:
 

delray

Well-Known Member
#26
cfh, here is the down fall with the slant intakes that I have found. well at least on the 4hp slant intakes
they are very restricted and will need some attention first before you really can take advantage of them.
has you can see the casting design really restricts the flow.




need to weld the casting up and then you can go back and port the intake out …….:thumbsup:


 
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#27
Very cool.

I have done the same thing on an 03 cobra blower plenum, I noticed it but figured it needed to be there for the bolt.
Do you use a short bolt or a stud?
 

delray

Well-Known Member
#28
yes massacre, still have about 3/8 length of thread to bolt up too. when the intake was welded up I kept the bolt in the threads. aluminum weld won't really stick well to steel..:thumbsup:
 

cfh

Well-Known Member
#30
I was looking at ebay for Dellorto stuff and came across an Indian made Dellorto MA19b carb copy for $29 (including fedex shipping.) It's advertised as, "Lambretta LI 150cc 19MM Carb". So i bought it. It's not exactly like a Dellorto UA19 unfortunately, but i think it should still work on a Tecumseh. The throttle on this carb is basically minibike ready. I'm not sure it has a choke though, that may be a problem. But i thought i would check it out. I'll keep everyone posted on this. Here's some pictures...







 
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#31
I have been thinking of going this route. I am looking for a carb that is not WOT at 1/4 turn like my tecumseh is. Don’t get me wrong I do love my Tec carb and it runs well so far but it would be nice to have some more travel. Do the slide mikunis achieve this? I seem to remember that they do but that was a long time ago
 
#32
Yes and no. I have a 22mm oval slide mikuni ( chikuni) on my hs50. The oval slide gives more throttle granularity than a true round slide or flat slide. It is a bit more carb than the motor needs but still works perfectly. From 3/4 throttle on power is the same as it can’t use as much flow as the carb supplies.
 

cfh

Well-Known Member
#33
non-minibike people really don't like the 1/8 turn from 0 to WFO on tecumseh carbs. The slide carbs in this thread do provide more travel. Not a ton more, but definitely more. from that perspective it is an big improvement. But i'm so used to Tecumseh carb travel, it really doesn't bother me. I have a Honda CT70 and frankly that's too much travel!
 
#35
non-minibike people really don't like the 1/8 turn from 0 to WFO on tecumseh carbs. The slide carbs in this thread do provide more travel. Not a ton more, but definitely more. from that perspective it is an big improvement. But i'm so used to Tecumseh carb travel, it really doesn't bother me. I have a Honda CT70 and frankly that's too much travel!
I’m used to it as well but would like to try something different.
 
#37
Patrick, is that the bike you took to windber about 4 or 5yrs ago. if so that little guy was so fast for a flathead.
I have to say that is the first flathead that really impressed me. remember that bike well on the trails.
rooster tailing dirt all day.....:scooter:
also randy had a mild little rupp that I like too. I believe mike has the bike now?


clear you mail box buddy. I got stuff to send to you soon.....[/QUOTE
Sorry about that. I haven't been checking in a lot, Just renewed my membership. Mail box should work again. Yes that is the same bike I had at Windber. Still running strong.
 

cfh

Well-Known Member
#38
Massacre got me looking at some other slide carbs. I tried a 20mm, which looked identical to the 16mm i have been using with great success. Unfortunately the 20mm just won't work on the Tecumseh HS50 motor. The jetting (out of the box) is incorrect. It will idle just fine, but it dies on acceleration. If you put the choke on about 3/4 way, it will work. But i don't see running with the choke on as a good solution. And besides all that, it didn't really perform any differently than the 16mm slide carb (which works pretty much perfect out of the box.)

I know there are jets available for these carbs. just i don't have any, and doing the jet replace experiment is time consuming. i would rather just buy the 16mm slide (for $12 !) and be done with it.

Note on both the 16mm and 20mm carbs the jets are not labeled. so i have *no* idea even what jet to put in to try (if i was going down the jet changing road, which i am not.) I did try putting the 16mm main jet in the 20mm carb, but it had the same poor-running result when using the 20mm carb on the HS50.

I have started experimenting with making my own intake manifold. Though using the stock Tecumseh intake manifold with an aluminum extender works just fine, having an actual intake that properly matches the motor and the carb seems to be ideal. Below is my first Tecumseh intake that I made. I could probably set up a jig to make these for people (in both Tecumseh 20 degree slant motor and flat motor varieties.) If that is something people would want, please post or send me a message (direct email best cfh@provide.net )

 

delray

Well-Known Member
#40
Massacre got me looking at some other slide carbs. I tried a 20mm, which looked identical to the 16mm i have been using with great success. Unfortunately the 20mm just won't work on the Tecumseh HS50 motor. The jetting (out of the box) is incorrect. It will idle just fine, but it dies on acceleration. If you put the choke on about 3/4 way, it will work. But i don't see running with the choke on as a good solution. And besides all that, it didn't really perform any differently than the 16mm slide carb (which works pretty much perfect out of the box.)

I know there are jets available for these carbs. just i don't have any, and doing the jet replace experiment is time consuming. i would rather just buy the 16mm slide (for $12 !) and be done with it.

Note on both the 16mm and 20mm carbs the jets are not labeled. so i have *no* idea even what jet to put in to try (if i was going down the jet changing road, which i am not.) I did try putting the 16mm main jet in the 20mm carb, but it had the same poor-running result when using the 20mm carb on the HS50.

I have started experimenting with making my own intake manifold. Though using the stock Tecumseh intake manifold with an aluminum extender works just fine, having an actual intake that properly matches the motor and the carb seems to be ideal. Below is my first Tecumseh intake that I made. I could probably set up a jig to make these for people (in both Tecumseh 20 degree slant motor and flat motor varieties.) If that is something people would want, please post or send me a message (direct email best cfh@provide.net )

intake looks good,making intakes for the hs-40 and 50's would be a good thing for people that don't have the ability,but depending the engine(hs40 or hs 50) will dictate the size of i.d. tubing and how it is built. for example a complete stock engine may run good with a 20+mm throat and a full built engine would little larger. for example after welding up my rupp intake was open up to about 22mm. then you get into the hs-50's with there funky intake port.
i think you should try a little testing with the 22mm mikuni/china carb. i and alot other members have very good luck with dialing them in from stock to modified engines. i can't say enough about them. they just work.....
pilot and main jetting takes the real mikuni parts.
 
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