My Honda Express at the time of purchase.
So you want your Honda Express to go faster. I thought over the next few weeks I’d perform some experiments on my stock NC50 to see how fast I could get it to go without using any performance parts (I do have a K&N hi-flow air filter). My top speed now is somewhere around 28 mph. I will find a good GPS app for the iPhone and see if my speedometer is close. Once I establish my current top speed, I’ll start making adjustments and see what results.
I was reading the service manual for the NC50 and saw that it called for 10W-40 transmission oil in the summer and 5W-30 in the winter. I’m currently running 10W-40 conventional oil and I think I notice some drag on cold days. I also read on mopedarmy.com (concerning the Suzuki FA50) that if you went from 20W-40 conventional oil to 10W-30 synthetic oil, you would obtain a 2-4 mph top speed increase. So my first top speed experiment will be to try a lighter weight synthetic oil to see if I obtain a noticeable speed increase. I’d be happy with 1 mph. I think 2-4 mph is a bit optimistic. I’m still undecided on what weight synthetic oil to try. I have 0W-20, straight 30W synthetic, synthetic transmission fluid. I also have conventional 5W-20 and 5W-30 oil. I probably have more if I dig around. Yeah, I’m an oil freak.
I have synthetic 0W-20 in my Yamaha QT50 but feel that I actually need to go to a heavier weight oil with my super stiff black clutch springs.
I’ll make videos of each top speed run and post them here. I’ve got several other ideas but will reveal them one by one as I make progress from test to test.
2/1/16 – Ok, just did a base speed test and hit 29.4 mph. Next step will be to change transmission oil and see if we get any gains or, worse yet, lose any speed.
Ok, I changed the transmission oil to 5W-30 and lost 0.9 mph. Top speed of 28.5. I’m going to look at changing the jetting next.
8/6/2018 – So I kind of lost track of this thread and thought I’d pick it up again. Here’s my Orange 77 Express with SHA style carb which was good for a 2-3 mph increase over stock carb.
I used a 65 main jet and it seems to be pretty dialed in. You can get Dellorto jets in increments of one so I could experiment with a 64 or 66 main jet. If anything, I’d try a 66 main jet next. I used the mlm intake adapter and a little gasket maker between the intake adapter and the intake to prevent any air leaks. If you don’t use a gasket or gasket maker, you’ll need a bigger main jet. When you increase top speed, make sure to upgrade your brakes with new pads, new cables, lube old cables, etc. New tires may be in store for you as well.
I might stick a performance exhaust on this next to see how it does. Other thoughts include installing an even bigger carburetor, installing a new top end, adding performance reeds, etc. But I’m not sure how far down the rabbit hole I want to go on this one. Stay tuned.
11/15/18 update:
A 69 jet seems better for that Orange Express. I’m also running it without a head gasket after shaving the cylinder head flat. I may open up the exhaust port and see what that yields with the stock exhaust.
12/1/18 update:
Ok, so I put a DR kit on the Orange Express. It has a 15.15 SHA clone carb and currently running a 75 main jet. It still has the stock exhaust which may be a huge limiting factor. I replaced both crank shaft bearing seals prior to installing the kit. I’m still breaking it in and have encountered and overcome several hurdles already. The header on my stock exhaust is kind of beat up so I’m running a double exhaust gasket to seal it up. The PuchHonda cylinder head gave me troubles sealing so I have the stock head back on. Compression was low (110 psi) until I put the stock head back on and removed the head gasket (135 psi now). I hope compression gets better as the rings seat. Low end was miserable at 110 psi. I’m hoping an extra 25 psi helps out quite a bit.
Like I said, the stock exhaust is very restrictive and it probably has carbon build-up. I’ll continue to work with it before trying a different exhaust. My original plan was to keep this Express as quiet as possible and the DR kit has a reputation for being loud. I thought the stock exhaust might help in this regard.
2/8/19 – Ok, I gave up on the DR kit/stock exhaust combo. That is just not going to work well. I’ve began another Express speed project. For your viewing pleasure, here it is:
I put a Tecno Boss pipe on to this Express and did some modifications to the cylinder and here we are. Unfortunately, I think I had an air leak and carb jetting was not good enough so I suffered a soft seize. But no worries. We are back up and running. I achieved a top speed of 39.7mph which I consider amazing on a stock cylinder. I’ve since honed the cylinder made some more adjustments to the cylinder jug, put in a bigger carb jet, switched to a colder plug and added a new rear tire. We are ready to rock as soon as the weather cooperates. Listen to her now:
Honda Express: back for the attack!
I’ve heat cycled it several times and will take it on some break in rides as the weather cooperates. The immediate goal is to break 40 and then shoot for 45 mph. Stay tuned.
Honda Express with tecno boss exhaust and 1.5mm cylinder spacing. 40.1mph.
Svader-rater nc50 vs. Black qt50