70cc PA50 Parma Kit with 15mm Del

_Sorry for the lack of pics, I didn’t have a camera available at the start of the project._

First impressions : Kit comes is a small box, minimally packed, but sufficient; all gaskets, wrist pin, and clips included; no instructions. My single piston ring was broke upon delivery, but benji hooked up another well before I was ready for it. There are some rough spots from molding on all the transfers and ports; the exhaust port has an offensive lump and de-compression port both of which will need to be eliminated. Impressive port map, overall exterior finish is nice, cylinder wall finish is also nice. Transfer and ports are noticeably larger then the Malossi kit and stock cylinders.

Install : I was in a hurry and really didn’t feel like rebuilding the Express drive train so I took the lazy man’s approach to case matching. First I lined the crank webs and bottom of the case with tissue paper just enough that nothing could get in there; then I took a small amount of play-dough lined the bottom case tightly with about a 1/8" thick layer. Then used some short 6m bolts to hold down the base gasket, once lined up I marked my cuts. All three transfers needed a good amount of work. I used a pointed tungsten bit to do most of it and finished with some red grinding stones.

The cylinder studs were bit smaller then the holes on the kit, I was able to shim two of them with brass tubing from Ace which got it centered pretty well.

The piston went on as smooth as could be, with a nicely lubed pin.

After lubing the piston and cylinder with some 2 stroke I installed the cylinder, making sure the ring stayed aligned on its pin. I installed the head gasket, and then a stock 77 NC50 head, and tightened it up in a crisscross pattern while turning the fly wheel. I finished up the install with a BP7HS plug.

Carb : Now after having the kit on a really seeing the potential of this cylinder I took a step back and decided to rethink the carb situation. The stock 12mm was just not going to cut it, not mention the silly jets (this had a later model carb with the o-ring style jets). So I had 15mm del knock off with an intake sitting around and started brain storming. This is what I came up with.

I took an intake manifold from an 80 NC50 and sawed off the top almost right thru the middle of the stock opening. Then I lined up the Del intake so that it was as centered and lined up to be matched to flow well, then drilled the needed mounting hole to bolt the intake to the other intake. For the top of the intake I took a piece of copper pipe that was about 16mm OD and bent the ends to match the shape of corresponding intake, put it in a finger tip of a rubber glove and stuffed it with paper towel until it had the shape I wanted my intake passage to have. Then I put the plug in place and molded Quik Steel tm tightly around the plug and against both intakes. I let the Quik Steel set for about 5 minutes and then removed the Del intake and the plug, then I let the Quik Steel set over night. The next day I planed out my intake design and went to town with the Dremel. I wanted to add some volume to the intake and I wanted to improve the flow thru the corner, as you can see in the pictures below I think I accomplished this rather well. After getting everything matched up I put it all together sealing all mating surfaces with blur RVT and allowed it to set another 24 hours.

Installing the carb was straight forward, removed the old intake installed the new intake. The stock throttle end was a little big for the Del, I simply trimmed about 1/16" off the end of the knarp and it worked perfect. As for jetting I guessed; I went with a #63 orifice drill. As for a filter I used a shimmed up uni-pod from one of my old RD 34mm Mikuni carbs.

Exhaust : The stock exhausts on any Express are junk in my opinion so that was clearly not an option. At my disposal were 3 clear choices; first there was the Leo Vince Circuit, a very nice pipe with the most impressive header of the bunch and great reputation but sadly no stand clearance; next was the Proma Lowboy Polymer, by far the lightest of all of them, close to stock header and not that impressive of a chamber, but no clearance issues but needed to a support bracket made; and the final option was a pocket bike exhaust that I had already modified to fit on the NC which has huge chamber, stock header and known performance qualities.

I went with the last as it was the easiest and I felt it matched the bike the best.

I did forgo the exhaust studs for some allen head bolts instead.

First start/ride : I turned on the fuel, put on the choke, wound it up, pulled the rear brake, and it turned over smoothly but no fire. So I wound it up again, pulled the brake and instantly she fired up; I quickly popped the choke and she began to idle perfectly. I instantly began checking for air leaks, and thankfully found none. I then did three 10 minute heat cycles. After rechecking all nuts and bolts I took it for a 10 mile cruise at

Re: 70cc PA50 Parma Kit with 15mm Del

The title got cut off it should read:

70cc PA50 Parma Kit with 15mm Del’Ortto Carburetor on a '77 NC50

Re: 70cc PA50 Parma Kit with 15mm Del

Holy snot. Thanks for all of this info!

77 NC50 Express w/70cc PA50 Parma Kit + 15mm Del

I forgot one very important step to the install section.

> After port matching I blew out the case with compressed air to get any loose chunks out; then I packed a small amount of play-dough on top of what was already there to lock in any small shaving; finally I carefully removed all the play-dough and tissue paper from the case and I blasted out it and crank with a bunch of carb cleaner followed up with some shot of high pressure air. Now it was ready to install the kit.

Re: 77 NC50 Express w/70cc PA50 Parma Kit + 15mm D

I love the Play-do Idea. Ive never seen a kitted express before. very cool. I would love to see pics. There arent any up yet, post em up!

Re: 77 NC50 Express w/70cc PA50 Parma Kit + 15mm D

nice write up but there is no reason to not run at WOT if anything its a bad idea to not hit every part of the power band in break in. Most break in ideas are a myth.

Anyways nice write up. I wouldnt' want to do 40 on one of those small ass things though O.o

Re: 77 NC50 Express w/70cc PA50 Parma Kit + 15mm D

See the word document to see it without formating changes, and photos are attached at the end of said document.

Sorry about the pics, just haven't had time to set-up a photo hosting account.

Corrections due to formating errors:

First start/ride : After checking all nuts and bolts I took it for a 10 mile cruise at 1/2throttle, it was 4 stroking and felt rich so I felt safe. Then right before I got home I did 1/4 mile stretch at just over 1/2 throttle and did a plug chop. It was rich just as I had suspected. I happily parked it for the night.

50 mile report : I’ve been bringing it close to 3/4 throttle and it’s impressive to say the least. The stock speedo only reads to 30mph, but I paced my Girl friend ridding it with my MB5 and she was holding 40mph solid just blipping above 1/2 throttle.

Re: 77 NC50 Express w/70cc PA50 Parma Kit + 15mm D

awesome, i should have done this when i did the DR kit last fall. make sure everything is loctite-ed to hell because every single nut, bolt and washer will fall off within a few minutes otherwise.

i've also had a hard time with the flange tearing off the stock pipe which i cut-and-welded.

i'm sure the carb makes a huge difference, the bike i built has had nothing but stupid carb problems since. i think the worn out jet o-ring sporadically leaks. any source for these?

70cc PA50 Parma Kit with 15mm Del

I vote that you bring this bike to South Dakota.

Re: 70cc PA50 Parma Kit with 15mm Del

holy shit, i think i care about my express again...

this might be my winter project. my express has a fresh set of brakes so i might wanna take this on.

Re: 70cc PA50 Parma Kit with 15mm Del

Update: I installed Boysen dual stage reeds (heavier set for modified engines) last night, no test runs yet but she fired up first kick. I'll be taking it out tonight for actual testing and I'll report back tomorrow. Once I find another reed block I plan on modifying it as well.

Graham - Try your local honda dealer, I got one a few years back from mine; or just upgrade, I'm thinking about going up to a 19...

Dustin - We'll see I don't think my bodies up for 60 miles on this thing.

Nash - Do it, you'll find a whole new love for it!

Re: 70cc PA50 Parma Kit with 15mm Del

Boysen reeds work great, a little bit better throttle response, seemed to run a bit leaner. I'm thinking of getting the low-end carbon ones instead of the dual stage, more acceleration would be awesome.

I went almost WOT last night, I'm thinking 45-47 is going to be about the top-end for this set-up, which is fine with me.

I also changed out the trans 10w-40 for some 20w-50, seemed to help the take off and is running slightly cooler.

Re: 70cc PA50 Parma Kit with 15mm Del

Are these the same reeds that are used for the PA50?

Re: 70cc PA50 Parma Kit with 15mm Del

Yup, PA50 reeds...

Re: 70cc PA50 Parma Kit with 15mm Del

My Express is still the ugliest motorbike in Pittsburgh, Derek, but now that's only because yours is far away.


Nice epoxy work! It's got the same "don't care how the outside looks as long as the shape inside is perfect" aesthetic that I consider to be a mark of quality on old Honda engines.

I had to think in exactly the opposite way when I made a new float for my Puch out of a film case some epoxy putty and a carefully-ground nail. We're letting a lot ride on this stuff being gas-safe, no?

I highly recommend epoxy putty (which comes in even more film cases!) for operations like this one where you need to hand mold something. Just remember not to get the five-minute-set kind if you're doing really finicky work...

P.S. - It looks like you've disabled the injector and are running premix, right? Did you change the fuel/oil mix for the break-in period?

Re: 70cc PA50 Parma Kit with 15mm Del’Or

I did use the putty type (quik steel) that you mold, it's gas safe; there's no way you could do that with regular JB.

Yup premix 40:1 for break in; 120 strong miles so far, still jetted rich..

Re: 70cc PA50 Parma Kit with 15mm Del’Or

Just a quick update:

-reinforced the exhaust/fender mount

-300+ miles so far, not a single seize and blasting 42+ all day long for miles and miles. Still running 40:1 syn. on the same jet, I'll be down jetting once the temps come up a bit.

-H4 bulb finally burnt out after 3 years of use and only after both tail and brake lights were long gone.

Re: 70cc PA50 Parma Kit with 15mm Del’Or

Hey Derek, what size jet are you running in this beast? Seems like I have mine set up pretty close to yours and I am just trting to get a starting point on what jet sizes to start with/order.

P.S. awesome idea with the playdough. Nice write up and keep us posted on the next breakthrough in express tuning.

Re: 70cc PA50 Parma Kit with 15mm Del’Or

Just noticed there's an issue with the word document attached so here's a PDF version, please disregard any spelling and grammatical errors.

Re: 70cc PA50 Parma Kit with 15mm Del’Or

Downhill Harvey (OFMC) /

Do you have a link to that exhaust?

Re: 77 NC50 Express w/70cc PA50 Parma Kit + 15mm D


That is a sick jawn derek

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