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 Post subject: PW80 Carburetor
PostPosted: Mon Jun 17, 2013 4:50 pm 
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Joined: Mon May 24, 2010 10:53 pm
Posts: 29
Alright, so I've posted some stuff on the mopedarmy forums, but I'm deciding to post this here. There's just something about some of the people at that place that turns me off. It's hard to have a real discussion there without children chiming in.

So I've been looking for a replacement carb since my 15.15 sha broke. It was a clone, and it had some stress cracks around the mounting point when I got it. It never wanted to seal right (my guess is the plastic sleeve), but I guess with all my loosening and tightening those stress cracks became worse and cracked.

I didn't like the way it was anyway, I bought it at a time when I didn't know much about motorcycle carb designs and I've had several motorcycles since then, and after reviving my moby project is has been a dissapointment with only one jet and adjustment screw to say the least.

So I started my search for a decent carburetor at a budget price and I came across a copy of a mikuni carb for the pw80. It's a clamp style carb which I believe is 15mm. The brand of the one I got is Wabron. The casting is good, not super clean but it's not much different from some of my original mikuni's or keihin's and it looks fine. Has a nice sturdy feel to it. It came with two mikuni style jets, both unmarked. I believe the main is in the 120-130 size and the idle is 15, as it's supposed to be jetted for the pw80. It uses standard 4/042 mikuni main jets and the normal 14mm idle jets. It is made for a two stroke so I believe the atomizer or whatever is set for that.

The ID of the manifold clamp is about 25mm without the plastic sleeve. With the plastic sleeve it's about 21mm, inbetween 20-21mm. I haven't mounted it yet but I believe you could buy a phbg plastic shim and it would fit to mount on that style of manifold. It also seems you might be able to use a 1mm shim for the dellorto sha inside the sleeve it came with to mount it on a sha manifold.

I'm ordering jets for it and the shims and possibly a phbg manifold so I'll report back what my findings are as far as mounting and performance wise. I'm pretty sure it fits and won't rub on the frame so I don't think mounting it is going to be a problem, but I'll report back whatever I find out.

I took some pictures of it's externals and internals, take a look:

Image

Intake side with sleeve.

Image

Adjustment side.

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Inside the float bowl.

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Slide, choke, Inside the top.

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Jets.


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 Post subject: Re: PW80 Carburetor
PostPosted: Tue Jun 18, 2013 2:37 am 
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Joined: Tue Apr 01, 2008 11:03 am
Posts: 937
Location: Rotterdam, Holland
At least it has the advantage of the choke plunger. Adding gas to the airstream, rather then really choking it, so you get richer-, but less gas, as with the SHA.

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Motobecane: Enfourcher la liberté!


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 Post subject: Re: PW80 Carburetor
PostPosted: Tue Jun 18, 2013 2:26 pm 
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Joined: Mon May 24, 2010 10:53 pm
Posts: 29
I forgot to also mention it came with the drain tube and that gas filter you see in the pictures, haha. Also in regards to an airfilter, it has a 32mm lip on the end and the shaft before that is 30mm. I bought a spacer that seems to be a good fit if you're using a sha carburetor. I got a rubber spacer, 3/4 in. ID and 1 in. OD. It was pretty snug but it fits in the intake side pretty good without the plastic sleeve. It's also pretty tight on the manifold. The spacer I got was 1 inch in length so that's why it sticks out like that, I'll trim it when I really mount it to test it out. I also bought a 3/4 in. ID x 7/8 OD spacer to see if it would work with the plastic sleeve it came with and it was too big by 1-2mm. I'm waiting for my order of jets and other stuff to come, will probably be here tomorrow or the next day. I'm tempted to try and find something locally as I don't want to wait.

Here's a pic with the spacer in the carb:

Image


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 Post subject: Re: PW80 Carburetor
PostPosted: Wed Jun 19, 2013 4:09 pm 
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Joined: Mon Dec 10, 2012 6:26 am
Posts: 578
Location: London
Interesting stuff! Keep us posted with the results.


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 Post subject: Re: PW80 Carburetor
PostPosted: Mon Jun 24, 2013 8:25 pm 
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Joined: Mon May 24, 2010 10:53 pm
Posts: 29
Alright so I finally got my order from treats, I haven't ordered from them in a while but it took a lot longer then it used to a few years ago, I guess they're a little more busy now.

So my rubber mount I tried before didn't really work well, but I found out that it mounts perfectly with the supplied plastic insulator and the 1mm dellorto sha sleeve. I haven't tried it yet but I'm sure the phbg shim will fit in it on the bigger manifold.

I also found out that while it does use the normal mikuni idle jets, the normal mikuni main jets don't fit, atleast the one I got from a local store. I believe it takes the larger 8mm (5.85 thread) jets VM 11/22, they're also listed online as minarelli jets in some places.

After I got rid of the airleak with the shim it seemed to work pretty good but needed some adjusting. Unfortunately I wasn't able to do much with it tho' cuz I blew my head gasket shortly after getting it running.


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 Post subject: Re: PW80 Carburetor
PostPosted: Mon Jul 15, 2013 10:45 am 
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Joined: Mon May 24, 2010 10:53 pm
Posts: 29
Alright so I've been using it for a while and I'm quite pleased. It was difficult but I got rid of all the airleaks on the intake and it's been running good since. I haven't got the jetting done yet (still using waay too big jet), but I'm easily hitting 45-50mph range with 74cc airsal and a restrictive stock exhaust. Throttle is excellent and I got a lot of power in the low-mid range. I was using a 54 tooth sprocket but I went down to a 44 I had. Lowered the rpms and boosted the top speed a little. I have alot of hills in my area and it climbs them with ease. I still got alot of tuning to do but I know it uses 6mm jets now, I'm gonna find out if 6mm dellorto jets fit since they're cheaper then the mikuni. I also have a small leak at the head gasket that needs to be fixed aswell.


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 Post subject: Re: PW80 Carburetor
PostPosted: Mon Jul 15, 2013 12:51 pm 
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Joined: Tue Apr 01, 2008 11:03 am
Posts: 937
Location: Rotterdam, Holland
great update. If the Dell'orto jets fit, it seems to be a good carb.

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 Post subject: Re: PW80 Carburetor
PostPosted: Wed Jul 17, 2013 12:32 pm 
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Joined: Mon May 24, 2010 10:53 pm
Posts: 29
Yeah I'm quite pleased with it. Obviously there are some things to watch out for, be careful when tightening the screws and make sure not to be too rough since it may not be as well made as some other carbs, but that's what you should expect for only 20 bucks. But if you're looking for more tunability then a dellorto sha for a budget price it's a good choice. It also allows people who don't want to run something as large as 19-21mm another option aswell. I'll see if I can get some pictures of it mounted when I get the chance.


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 Post subject: Re: PW80 Carburetor
PostPosted: Fri Jul 19, 2013 2:40 am 
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Joined: Mon Dec 10, 2012 6:26 am
Posts: 578
Location: London
I'm glad that you've made good progress with the carb, and thanks for sharing the info with us. Look forward to the extra pictures!


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 Post subject: Re: PW80 Carburetor
PostPosted: Thu Aug 22, 2013 3:05 am 
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Joined: Mon May 24, 2010 10:53 pm
Posts: 29
So the carburetor was working good but I was having problems with the carb staying on the intake. It would be on it good but after a while it would start to want to twist around or loosen, but I found out some things that I think would fix this. I will say when the carb was mounted good with no air leaks it ran perfectly. I was riding it around town all over the place with no problems.

Some motorized bike websites sell this same carburetor (for like twice the price), but on those websites I believe they come with a different spacer which I think would mount onto our 19mm (sha) intakes perfectly. I found a website that sells them seperate here and I'm gonna pick one up to confirm this. I can tell from the picture on the website it's thicker then the one that came with mine.

If anyone is interested in what my set up was, it was this carb, 84 main jet with the stock idle jet, 74cc airsal, stock exhaust, no air filter. Would hit around 45+ easily. Spark plug was a nice chocolate brown. Umm, what else to say... One of the main problem with the carb is where the fuel inlet is, you gotta route the fuel line right or the cylinder fins might burn a hole though it. I did notice that some of the motorized bicycle websites sell this same carb with a different fuel inlet placement.


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 Post subject: Re: PW80 Carburetor
PostPosted: Thu Aug 22, 2013 3:19 am 
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Joined: Mon May 24, 2010 10:53 pm
Posts: 29
Here is a link to an example of the same carb with a the different fuel inlet: http://www.ebay.com/itm/CNS-High-Performance-Carburetor-for-80cc-66cc-48cc-Motorized-Bicycle-/

Here is also a forum post talking about making a better bushing: http://motorbicycling.com/showthread.php?t=30179

It actually seems like the bushing seems to be the issue everyone has with these carbs, so I'm not sure if the one I posted before would be good, but i'm sure it's better then the one I got with it originally which was definitely too small. If you're handy enough you should be able to get it to work out.


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 Post subject: Re: PW80 Carburetor
PostPosted: Fri Aug 23, 2013 10:23 am 
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Joined: Mon Dec 10, 2012 6:26 am
Posts: 578
Location: London
Thanks again Insaniac for keeping us up to date with your progress, and useful info regarding the bushing. Hope everything is fine now with your replacement carb!


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 Post subject: Re: PW80 Carburetor
PostPosted: Fri Aug 23, 2013 4:05 pm 
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Joined: Mon May 24, 2010 10:53 pm
Posts: 29
Alright so I didn't buy that bushing I posted earlier because I found a better way (atleast I think). You can by nylon bushings (I think) from mcmaster carr, or whoever your supplier is that work perfectly. They're 3/4in ID 1in OD, all you have to do is cut a slit and it works perfectly on the sha intake. It cost like 6 bucks for a pack of 5. After I put this on and tightened it (be careful and not tighten it too much or it might break) and it worked perfectly, nice and snug and I don't think I'll have the problems with it loosening like before. Here's a pic of what you can get:

Image

So I was having some problems with it starting and stuff before, but I realized it was my sparkplug. I put a new one in and it ran like 10 times better. Starts right away and has more power all around. I was surprised how much of a difference it made and why I didn't realize it sooner. I gained around 5mph and I'm hitting around 50mph pretty easily. I also hammered this piece of brass pipe into my exhaust around where it broke, so now it doesn't vibrate like crazy anymore and is alot quieter. I'm still looking to get something better but for now I'm pretty happy. I was driving it around earlier and it runs like a dream. I took some pics of the engine, things aren't that clean right now but you can get an idea. I put a bunch of permatex motoseal around the top of the carb and where it connects on the manifold and around basically everything. I didn't do this because I needed to, just as a preventative measure as I don't want anything to happen when I'm driving around. I live uphill so it's a pain to push it back home.

Image

Image


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 Post subject: Re: PW80 Carburetor
PostPosted: Mon Aug 26, 2013 1:55 am 
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Joined: Mon Dec 10, 2012 6:26 am
Posts: 578
Location: London
It's all coming together and looking good Insaniac! Thanks for sharing the info with us.


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