HOT TIP...motorcycle type carbs on 4 strokes

atombikes · Nov 21, 2013

Slowbalt, thanks for the pics.

So as I understand this, all you did was rotate the carb on your horizontal mounted engine to show that the carb bowl doesn't interfere with the engine shroud, right?

Either way, thanks for going out of your way to verify this.

And it won't be a problem for the carb to be angled off vertical as shown in your second pic?

SlowBalt · Nov 21, 2013

F-rod, I never claimed this was my idea. I seed that I found this information on this forum.
I'm just trying to help others by making the info easier to find. Not everyone looks threw every build thread. Sorry if I offended you some how.

Sorry for the off topic .

SlowBalt · Nov 22, 2013

F-rod .Would you be willing to try to rotate your carb to see if it hits the shroud with the Shorty intake. So everyone can have the info.

chainmaker · Nov 22, 2013

Some nice helpful info here.

KCvale · Nov 22, 2013

atombikes said:
And it won't be a problem for the carb to be angled off vertical as shown in your second pic?

Of course an NT at a 90 angle will be a problem.

The NT carb is gravity fed and controlled, as soon as you turned the gas on it would just run out all over the place and keep running until the tank was empty at that angle.

As for if an NT or CNS will work on an HS 49cc 4-stroke I'll let you know as I just ordered a new HS 49cc engine only yesterday just to get the carb for a repair as everyone is out of the replacement carbs.

atombikes · Nov 22, 2013

KCvale said:
Of course an NT at a 90 angle will be a problem.

The NT carb is gravity fed and controlled, as soon as you turned the gas on it would just run out all over the place and keep running until the tank was empty at that angle.

As for if an NT or CNS will work on an HS 49cc 4-stroke I'll let you know as I just ordered a new HS 49cc engine only yesterday just to get the carb for a repair as everyone is out of the replacement carbs.

KC,
I don't think you understand what slowbalt was trying to show in his photo- I originally asked if there would be interference issues with a using the kit type carb and intake manifold on a Harbor Freight engine that is installed in a vertical configuration.....slowbalt responded with a pic that shows his horizontal-engined bike, but with the carb rotated 90 degrees to show there would not be interference issues between the carb bowl and the engine shroud.

My question is asking whether it is OK to run a kit carb as shown in slowbalt's second photo, which shows the carb will be about 20 degrees off vertical (left-right).

SlowBalt · Nov 22, 2013

It actually sits on an angle in the horizontal configuration as well. I've run around 50 mi now with no problems . When parked for a few days the float stuck once ,but a few taps with a screwdriver took care of it.

atombikes · Nov 29, 2013

OK guys, I'm on board with this idea.

Today I bought a billet manifold from Spooky Tooth (less than $15 on sale)

and this carb for $13 shipped direct from China:

http://www.ebay.com/itm/121055458786?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2648

Once I recieve these parts I will try to fit up the carb. I'm expecting (50/50 chance) that the straight billet intake will cause some interference issues, and if that happens I will get one of those offset manifolds for $7 shipped on ebay.

KCvale · Nov 30, 2013

atombikes said:
OK guys, I'm on board with this idea.

Today I bought a billet manifold from Spooky Tooth (less than $15 on sale)

and this carb for $13 shipped direct from China:

Once I recieve these parts I will try to fit up the carb. I'm expecting (50/50 chance).

Sorry, zero chance, that billet is for CNS carbs so you can take the plastic insert to narrow the instake to fit an NT header out.

The Z header however is the size of the NT carb intake so no worries.

The goal is to get the carb bowl as level to the ground on both planes as possible.
You can liken it to a full cup of coffee on an un-level crooked table, it will spill and never hold all it could.

Your jet is a straw in the middle that doesn't go all the way to the bottom.
You want the bowl as close to a level fill as possible and good fuel flow.

Speaking of fuel flow, if you have a tank filter and skinny fuel line you may find yourself loosing WOT or at least a lean condion at WOT even on a level carb as the jet end starts sucking air, this is really compounded by an un-level float bowl not to mention the float value itself simply does NOT like operating at angle, especially a left/right mismatch, they bind either stay closed or stay open.

You should be fine with a Z header pipe and NT carb.
Save the billet for when you run across a CNS carb AND your cylinder is at a 90 to the ground which isn't often and why I still have a couple in the carb parts box.

F_Rod81 · Nov 30, 2013

It will work! I'm pretty sure he ordered the proper manifold. With a little modification it will work flawlessly with NT, RT, and or speed carburetors. Same goes for the CNS manifold; it's compatible with the right parts to bring it all together. (^)

atombikes · Nov 30, 2013

The intake is only listed as a "Manic Mechanic" billet intake....no size or indication of the type of carb listed on the SpookyTooth website. I guess I assumed the intake dia to be the same for all these type carbs?

silverbear · Nov 30, 2013

I made the same assumption and also took advantage of the sale. Since I have the same billet and same carb on order we'll find out before too awfully long, eh?
SB

atombikes · Dec 1, 2013

SB,
Kinda funny we did the same thing. I read somewhere (I think it was in a vendors website) that if you have an intake that needs shimmed out a little, wrap the intake with some electrical tape and it'll make a good seal.

Also just thinking out loud, if I put a 90 degree elbow on the end if this manic intake (and then put the carb on the elbow) , doing so would allow the carb to sit level in both planes . Question is, what size elbow? I'm thinking copper plumbing fittings it something similar

atombikes · Dec 1, 2013

Crap.

If I understand the original posters writeup, the billet intake he used had 40mm spacing between mounting studs; but the 4 stroke engine had 38mm, so he had to mod the intake. OK.

Digging on the Manic Mechanic website, I found this pic:

the one I bought:

Comparing that against the pic of the intake SB and I both purchased, looks like our intakes are "Standard Shorty" not "40mm wide studs"....the mounting holes on the standard are much closer together (meaning it probably won't mount).

What engines require the 40mm spacing for the intake manifold?

KC, I see what you mean about the CNS manifold being different.

atombikes · Dec 1, 2013

SB,
I went back to the well at Bikeberry and got this manfold for $2.97:

http://www.bikeberry.com/engine-kit-parts/fuel-components/40-mm-intake-manifold.html

It seems to have the best-compromise offset orientation (with respect to the mounting studs) required for the vertical mount engine config, and the correct 40mm spacing.

KCvale · Dec 1, 2013

atombikes said:
Crap.

If I understand the original posters writeup, the billet intake he used had 40mm spacing between mounting studs; but the 4 stroke engine had 38mm, so he had to mod the intake. OK.

KC, I see what you mean about the CNS manifold being different.

When I bought mine that was all MM made and he made it for the CNS, didn't know he was making smaller ones now but it makes sense.

I can't recall offhand what motor kits use wider intake and front mount stud spacing but there is at least one.

Atombikes, that Z intake works just dandy with a little forward leaning cylinder and what shipped with Skyhawk kits to accommodate the lame air cleaner on the CNS II carbs which I really like on a 66cc better than an NT, but the NT rules on a 48cc.

For example this build like most has a forward leaning cylinder and Z off-set it just to be level and allow room for the air cleaner.

With an NT you should be able to just use a standard short angled intake unless of course you have clutch cable issues and they don't seem to hamper performance in any way.

scotto- · Dec 1, 2013

KCvale said:
With an NT you should be able to just use a standard short angled intake unless of course you have clutch cable issues and they don't seem to hamper performance in any way.

I don't think there will be any clutch cable issues on a 4-stroke engine

I don't even notice the carb angle.....my eyes are drawn to that barnacle perched on top of the already massive top tube lol. Can't that p-nut at least be mounted inside on the down tube to give the bike a more balanced look?

Sorry but that tank is just killing the good looks of the rest of that bike....honestly.

Fatandre · Dec 3, 2013

Could this be done to the huanshen engine?

chainmaker · Apr 6, 2016

I know the thread is a little old, but what was the verdict on an off the shelf carb intake to run the HF79 vertical.

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HOT TIP...motorcycle type carbs on 4 strokes

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