DanielO's Honda Elite Sprint/Drag Scooter!

It's show and tell for your custom scoot! Post photos of your project scooters, etc.

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DanielO.
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Joined: Fri Sep 07, 2012 1:19 am
Location: Efland NC

Postby DanielO. » Fri Dec 21, 2012 1:36 am

Hey! thanks for posting those pics Josh... Its strange how in the second pic the transfers don't look symmetrical... oh well...

I spent several more hours today working on the skirts of the jug and the piston...there was a fair bit of material blocking flow when the piston was at bottom dead center... I also opened up the boost port window in the piston and drilled some oiling holes where there was some evidence of scuffing...

overall, I'm happy with the condition of the engine.... there's easily 35-40 actual 1/8 mile passes on it, as well as 20-30 dyno runs, and lots of hooning around in the yard and doing burnouts in the garage.... testing the clutch setup.. etc..

hope everone has a good christmas and happy new year!

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Areomyst
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Postby Areomyst » Thu Feb 21, 2013 11:44 pm

I'm curious to see what you gain out of this Daniel! 9.24HP before, and now youv'e done porting and some more tweaking, on top of the stretch for less wheelie action... I'm looking forward to it! :D

~Josh
"The more a man learns, the more he realizes how little he knows."

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Areomyst
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Postby Areomyst » Sun Mar 03, 2013 10:52 am

Daniel brought his little dragster by for show and tell yesterday!

You can see the nice job on the stretch in the below photos, but there are also a few pleasant surprises...
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"The more a man learns, the more he realizes how little he knows."

DanielO.
Posts: 180
Joined: Fri Sep 07, 2012 1:19 am
Location: Efland NC

Postby DanielO. » Wed Mar 06, 2013 2:55 pm

Just a little bit of info for anyone curious.... the carb is a Walbro wb23. it has a 26mm throat, and is very similar to what Kart racers use on the KT100 yamaha..

Its running real nice with the low speed screw about 1 1/16 turns out and the high speed screw at about 3/4 turn out... but I have not put load to it... dyno time coming soon..

I decided to stretch the subframe and weld it directly to the main frame of the scoot.. partly from the tendency to wheelie, and partly because there were two pivots between the frame and the engine so when the clutch engages the whole engine would rock upward and misalign so bad the tire would hit the spring... it pushes nice and straight now.. should be worth a little on reaction time..

Nathanael
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Postby Nathanael » Wed Mar 06, 2013 5:16 pm

Curious about the carb,looking at it I take it its a float free design? Do these use a diaphragm fuel pump? And are they an adjustable needle only setup or are jet changes still necessary? Also if it does use a diaphragm pump can it be utilised on any engine? Or do other things like vacuum etc need to be taken into account. Sorry for all the questions but I have been thinking about a setup like that on and off for a long time but never heard from anybody with direct experience of them.

Thanks

Nathanael

DanielO.
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Location: Efland NC

Postby DanielO. » Wed Mar 06, 2013 7:06 pm

No worries, questions are good!

the carb does not have a traditional float, but there is a chamber with a diaphragm that keeps a constant supply of fuel to the metering circuit in any position and under any forces acting differently than gravity... the kart guys use them because they see 2.5-3 g cornering and that will make a float carb surge...

there is also a fuel pump diaphragm that supplies fuel to the metering diaphragm and it requires a crankcase pressure pulse signal... on this carb there is a second hose nipple that I plumbed to the bottom of the reed block. basically the same port needed to open a vacuum petcock on the gas tank... It will LIFT fuel from 3 feet below the carb :shock: and that really suprised me...

the mixture adjustment is with the needles only, although I believe the carb body can be drilled larger if, for example you wanted to run methanol... a different needle may be necessary then also... I think I have plenty of headroom to richen my mixture more than enough for any future upgrades just using the needles.. it is rather sensitive, and can go from rich or lean to perfect in as little as 1/8 of a turn, but I'm used to that from many days of working on and using chainsaws, weedeaters and leaf blowers...

I think you could use a carb like this on any 2 stroke, as long as the engine demands enough air for the size carb you want to use.. I don't know about on 4 strokes... Walbro has a .pdf manual that details its operating theory and you can find that here

http://wem.walbro.com/distributors/serv ... series.pdf

or if the link dosen't work just google walbro manuals..

Nathanael
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Postby Nathanael » Wed Mar 06, 2013 9:46 pm

Thanks for the info,whats your opinion on ease of setting up compared to a delorto phbg or whatever?

I have a yamaha slider with piston ported minarelli engine and access is extremely poor to the carb meaning removal of airbox,carb from manifold and fuel/vacuum hoses etc to even get near the float bowl. I like the idea of things being adjustable externally. Just need to find some flow figures to see hoe they compare size for size,im assuming that butterfly will provide a significent flow impedance over a slide design.

I was running an airsal t6 70cc cylinder and doppler exhaust and seeing indicated speeds of 60mph on the flat and more downhill. (before it seized against the exhaust bridge)

Engine now has a dr 70 top end with exhaust widened and raised to 195ish degrees and transfers at 127 from memory-I cocked up while cutting hence the huge exhaust duration :D

same pipe which is good for about 10k peak,uprated crank, c3 mains and all transmission components replaced. Need to helicoil one of the bolt holes in the crankcase and sort an intake and carb.

Have seen a few on ebay so hopefully can find something at 21mm or so.

Your wee scoot looks fantastic by the way, like the 3 different carbs visible looking through your older posts :) nice to see another experimenter

DanielO.
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Location: Efland NC

Postby DanielO. » Thu Mar 07, 2013 12:56 am

I'll have to keep you posted on ease of setup... really, just getting the thing bolted to the engine was quite an adventure. I still have throttle linkage to finalize...
I think it will pay off at the track if conditions change or I want to add some silly spray...

I have been using walbros on outdoor power equipment for the better part of 2 decades, so tuning and rebuilding them is kind of second nature. hopefully this setup will prove as easy to tune as a Stihl or Husqvarna.. there's no comparison to slide type carbs for easy adjustments....

I have heard they are heavy on fuel consumption, but thats not an issue on a sprinter...

the WB3a that they use on karts is available new for around $100... here's one place I found that has them.... there are many others

http://www.out2win.com/catalog/walbro_wb3a.html

I paid $35 including shipping for two of these carbs, 8) so deals can be had..

here is a link to a site with all the walbro models listed with specs including venturi size...they don't list CFM though... i think the WB series is probably the best for our engines, but there are some others that have 17+mm venturis

http://wem.walbro.com/walbro/family2.asp

this bike was doing 55mph in the 1/8 mile before all the mods you see now.. :twisted:

I don't think 195 exhaust duration is too huge, I know of one bike that went from 11 to 15 hp by simply raising the ex duration from 190 to 194, and making the top of the port as wide as possible... and I even think that was on an airsal t6....

Nathanael
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Postby Nathanael » Thu Mar 07, 2013 12:19 pm

Interesting.....I have my eye on a wb19 at the right price, same size venturi though.It seems to be from a kart motor as well.

One thing I havent been able to find out is differences between the same series of carb wb19,wb23 etc. From what I can see there are only 2 different venturi sizes in that series despite a few dozen different models :) are you able to shed any light on this? Only thing I can think of is different needle sizes but don't see any way to differentiate between them based on spec.

DanielO.
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Location: Efland NC

Postby DanielO. » Thu Mar 07, 2013 1:59 pm

I think the different models with the same venturi size are all about how the throttle and choke are oriented...some have the shaft on the left, some on the right... some probably get their crankcase pulse through the flange that bolts to the engine instead of having a seperate nipple.. I think the only way to tell a difference is visually... and if you are modifying to fit your application then pretty much anything will work if you make it...

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Areomyst
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Postby Areomyst » Sun Mar 10, 2013 12:00 am

DanielO. wrote:I don't think 195 exhaust duration is too huge, I know of one bike that went from 11 to 15 hp by simply raising the ex duration from 190 to 194, and making the top of the port as wide as possible... and I even think that was on an airsal t6....


Blasphemy!!! :twisted: :roll: :twisted: I had to laugh out loud at that. I didn't catch it as I have only skimmed the recent posts in your build thread until tonight. That sounds suspiciously like one of my engines.

The curiosity of seeing how your Walbro carburetor works out is plaguing me! I know that you have spent a lot of time and thought on setting up your intake setup, and I hope that it is everything you wanted it to be, and more. I can't wait to see how this works out. I expect your engine to be up substantially on power.

Depending on how your carb works out for you, I may end up switching myself! I'm using a Stage 6 PWK 24 at the moment. Moving up to a 26 might not be a bad thing, and if the pumper carb is indeed that easy to adjust, then I don't have a good excuse not to give it a try.

Keep up the excellent work Daniel!

~Josh
"The more a man learns, the more he realizes how little he knows."

DanielO.
Posts: 180
Joined: Fri Sep 07, 2012 1:19 am
Location: Efland NC

Postby DanielO. » Sun Mar 10, 2013 9:39 am

:lol: yeah, maybe it is...

I still have to finish up the throttle cable, I replaced the entire housing but kept the inner cable... I gave up yesterday due to feeling ill.. better today, but still coughing alot... you should come by after the incriminators meet and check it out

ottoman
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Postby ottoman » Mon Mar 11, 2013 7:21 pm

Remember the 26mm Walbro has a lot more restrictions in the bore than a slide type carb of equal size.... once you get your flow bench working flow both to compare. On butterfly carbs we always ended up thining the shafts and rounding the screwheads and removing any extra sticking through the back of the shaft to increase the flow.. the extra flow is easy to measure on a flow bench.

DanielO.
Posts: 180
Joined: Fri Sep 07, 2012 1:19 am
Location: Efland NC

Postby DanielO. » Tue Mar 12, 2013 10:54 am

I'm stepping up from a 21mm so I should'nt lose any flow, might not gain as much as if it were a 26mm slide but we'll see... I'm just going to dyno it, and it will either make more power or it won't... .

I'll be sad if all that work was for naught, but at least I don't have a huge wad of cash in the setup...

I can easily go back to a slide carb with just a few bolts and a longer throttle cable.. When I modify things, I always like to make sure I can Undo what i did... and I never EVER throw anything away... :roll:

DanielO.
Posts: 180
Joined: Fri Sep 07, 2012 1:19 am
Location: Efland NC

Postby DanielO. » Fri Mar 22, 2013 11:12 am

Well, I had to switch back to my Mikuni to make it to the track last sunday... but It was no big deal...

I made just over 11 hp at about 11k rpm with my homemade pipe, got it all set up with three 7 gram sliders.. got to the track, waited in line, and then on my first pass, my pipe broke off at the flange and I was done... :oops: I was on the way to my best pass ever too... I ran 11.7 at 53mph with basically no pipe from about half track...

I admit that my welds failed probably because the bracket that mounts the pipe to the engine at the back only has stiffness in one plane... allowing the pipe to move left and right in relation to the engine...

I will fix up a new pipe with better brackets and test again, and with more time I will try the walbro again... It ran but wasn't being consistent, and I ran out of time... when I pulled it off, I found a very likely air leak at the base of the intake... so I think by fixing that it will work better...


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