New (hopefully) observation on weak HT 80cc motor - anyone seen this ?

[andynogo]

I have a lot of ideas - was thinking about rigging a tube extension for the exhaust so I can run it under my coat to keep me warm (it is cold in NH this time of year). And maybe some screws + bolts in the tires...

addict

Mate that's just about the funniest thing I've heard of in ages! I applaud your lateral thinking!

Oh and back to soldering jets- yes a small stock of jets to swap with would be good but I'm impatient and wanted it fixed NOW which is why I soldered. Most soldering irons will heat the jet enough to solder it- using resin core solder. I soldered it up and stuck the smallest mig tip cleaner (about .4mm) through the molten solder, then slowly opened it up to just under .5mm.

 

[AussieSteve]

Even normal resin-core electronic solder would be fine - no mechanical stresses involved. I tinker with hobby electronics. Standard PCB (circuit board) drills would work if you can drill without breaking them. No fine adjustments like 0.5x, but they come in 0.5mm, 0.8mm and 1.0mm.
These are available from electronic hobbyist stores. (In Oz, **** Smith Electronics, Jaycar, Altronics etc.)
If you have a dremel, (or similar), you're set. I only have a ~12W 12V mini drill, not enough guts. My 750W hand drill's chuck can't grip such thin bits.
Buying jets is easier. (Lazy, I guess)
I'm impatient too, but it gets easier to wait as I get older. (Don't know why, since it really means there's less time left to get everything done.)
... Steve

 

[AussieSteve]

Wow, censored! That's DSE, [short for Richard] Smith Electronics.
... S

 

[machiasmort]

Originally Posted by chrisnbush

I have a lot of ideas - was thinking about rigging a tube extension for the exhaust so I can run it under my coat to keep me warm (it is cold in NH this time of year). And maybe some screws + bolts in the tires...

addict

I thought I seen that in the Health Care plan, for old people tho....
Didn't want you to waste your money on a patent! LOL! Sorry for politics, was more a joke!

 

[chrisnbush]

Mate that's just about the funniest thing I've heard of in ages! I applaud your lateral thinking!

Oh and back to soldering jets- yes a small stock of jets to swap with would be good but I'm impatient and wanted it fixed NOW which is why I soldered. Most soldering irons will heat the jet enough to solder it- using resin core solder. I soldered it up and stuck the smallest mig tip cleaner (about .4mm) through the molten solder, then slowly opened it up to just under .5mm.

Man, this forum is great - thanks guys. I probably will try the solder approach, waiting for the jets anyway. Good to know you can get drills at hobby store, although steps between .5 to .7 would b nice from my read. There was a drill "jet set" on ebay a couple of days ago, but it expired - I am sure I can find them elsewhere.

Is there anything you have to do with the needle ? Seems like I might have to take emory cloth too it ? If it fits at .7 it won't at .5 I would think, at least the clip positions wouldn't make sense anymore right ? Hoping I can just stick the clip in there and have it work OK, but usually this approach (my most usual) ends in failure...

Thanks again

BigKid

 

[AussieSteve]

{Originally by chrisnbush}Is there anything you have to do with the needle ? Seems like I might have to take emery cloth to it ?

No, initially, you have to do nothing with the needle. (Unless you find that raising or lowering it helps with mixture.)
Take note that the needle jet and main jet are two different entities, the main jet, (the little one with a flat screwdriver slot), screws into the needle jet, (the longer one). Only the diameter of the hole in the main jet needs to be changed. There is no change to the needle jet's diameter, so do not sand or otherwise alter the slide needle. The taper is carefully balanced for mixture.
Good luck. Keep us posted.
... Steve

 

[chrisnbush]

OK, so I got the main jet off my "backup" carb and used a microtorch (I reallly like these things, bought it just for this, but can see a LOT of uses for it) to "solder it".

Wondering if I did it a good way. As it didn't seem real sturdy to apply solder to the shallow inverted "nozzle" side of the jet, I added it to the threaded side (with its much wider hole) essentially filling up the jet with solder. After doing so, I touched the threaded side to my grinder to flatten it out.

I purchased some carb jet drills on Ebay, and my plan from the info on this post (thanks guys) is to use a 0.6mm drill to drill in from the nozzle side 0.7mm hole all the way through the solder on the other side. Do you think this will work, or am I going to have to use a larger drill on the threaded side to drill back into the solder to make a "well" like there was before ?

Hey, I'm having a good time anyway...

BigKid

 

[AussieSteve]

Hey, I'm having a good time anyway
...BigKid

Having a good time is what it's all about.

the stock hole size is .7 mm

Are you sure of this, Ghost0? Tony Ciccio from Rock Solid Engines told me that the standard main jet size is 0.79mm. (66cc Series 3 from ZBox Australia, 1 month old, later type NT carby w/ coated slide)

Excerpt from Tony's email:-

the jet size for the carb I would recommend a .72 or .73 the jet which comes standard from manufacture in the carb is .79

Now I'm confused.
... Steve

 

[Ghost0]

Every one I have seen has been .7 mm, that doesn't mean that there are not different sizes out there.

As far as the solder method described this is not what I would have done but only time will tell if your method works. My thought is by filling up the threaded end you may have altered how the tip of the needle meters flow at idle and just off idle. I went the other way and just closed the hole on the exposed, non threaded side. Then I went and drilled it from the other side essentially using the existing jet hole to ensure the new hole was drilled straight.

 

[chrisnbush]

My attempts to resize stock HT carb jet

Well at least I learned something...

OK, so I got a microtorch (handy thing) and filled an extra jet I have with electrical solder (pic 1).

I then drilled out the threaded end with a 3/32 (sorry about the english) drill, to remove the bulk of the solder.
I reamed it with the drill a bit to make the opening more cone like. So far so good (pic 3 - the drill in this
pic is the 0.48 jet drill below, not 3/32 obviously).

I got a carb jet drill kit cheap on ebay, like 12 dollars with shipping. I never learn. The smallest drill in the
kit is 0.48 mm (as I measured with my digital calipers) so I started with that (pic 2 is drill set with chuck).

The chuck is a piece of chinese excrement, and it was difficult to get the bit to turn straight due to innacurate holding
of drill by jaws, and a little by inaccurate holding of chuck by my power drill jaws, but more the chuck I think.

So I started to drill through the jet (not threaded side). The drill was smaller than the hole, so the hole is at LEAST larger
than 0.48 ! But I quickly broke the drill.

Bullheaded I proceeded to the next drill size up that still fit in the hole, about 0.56 (all these measurements are in mm with my callipers).
Don't know why I thought that/ I would be able to drill out one drill bit (stuck in hole) with another of the same material.
It broke - sometimes I just don't think !

So BEFORE trying the next drill (about 0.62mm) I took my microtorch and tried to clean out the old solder, with the intent of resoldering.
I was trying to use the 3rd bit to push the material out through the jet. Couldn't get the solder out, it hardened somehow under the torch
and probably the old bit was stuck in the jet preventing it.

So, thinking maybe I had softened it up, I tried drilling with the third 0.06mm bit and that broke too.

By the way, I sized the jet the best I could to be 0.68 - 0.72mm - although this wouldn't be much different than 0.79 with the tools I am using. I did this by measuring the bit that just fit with my digital calipers, none
of the bits being marked (too small I guess). The kit description was "12 bits sizes 52 - 74. What the heck does that mean ?

Well, for more entertainment value I have also attached pics of my two rides - my centermount (the object of this effort), and my DAX rear mount
Titan cruiser. The titan is my commuter, but the centermount is my toy. If I can just get it to run a little leaner at high RPM, as
I mentioned before I have the needle on the lowest setting.

So I went out and spent 30 dollars getting 3 of these tiny jets from Dellorto (mostly shipping). I am getting 0.65, 0.60 and 0.55. I will let you know

Enjoy the ride

BigKid