Follow along for custom 150cc honda nice.

[fatcaaat]

I recently started on the build out of a Nice 150. The starting point was a complete engine core from Thailand that had 55000km on the clock and the bottom cases had never been split. The insides of this were filthy. The engine did shift through the gears and had compression but i did not attempt to start it.

Inspection revealed some interesting items. The crank seemed in spec. Bearings looked ok. Cylinder was at third overbore. Valve train looked ok. Counter sprocket worn out.

 

[fatcaaat]

I never trust something like this so you always replace the crank pin and bearing. I am doing a stroker pin on this so it was coming apart anyway. This is where builders go wrong and the trust its ok by doing the side to side and in and out spec check. This checked out. But look at it.

 

[fatcaaat]

Won’t bore everyone with cleaning details but will give this boring photo. This is the largest you can bore nice or small block cases without offsetting toward the bottom. This bore is 59.1mm. Absolutely the max. I will be using a 56mm bore. The first version will be stock head, ported, with cam. A future version will likely have a tb roller rocker head.

 

[kirrbby]

Stock stroke is 55.5mm. What will the new stroke be?
Crazy amount of wear on that pin. 55,000km huh??! 34,000 miles

 

[fatcaaat]

3mm pin and 97mm rod will make a 61.5mm stroke.

 

[kirrbby]

3mm offset, must be. That's crazy big...to me.
I consider 54mm to be a long stroke. So a stock nice 55.5mm is crazy big already.

 

[fatcaaat]

My trp engine runs 66mm stroke. That big stroke lets you run low rpm at cruising speed and seems to broaden the torque band. I suspect a 150 won’t be much faster than my 127 dohc but will be fine with me lugging it in fourth gear at 3k rpm.

 

[fatcaaat]

After a little over a month of waiting, I have finally received the parts I need, or thought I needed, to build the stroker crankshaft. Unfortunately, when I purchased the stroker pin kit, they did not include the necessary split bearing, so I can install the connecting rod. That meant I had to re-order from Thailand a few sets of the split crank bearing, so this can be put together. I’m not exactly sure why they would sell the pins without the bearings, but it is not a cost thing as the split bearings are only $10 each. The connecting rod is 97 mm which is 3 mm shorter than the standard Honda nice connecting rod so that the deck height remains the same. I prefer to do it this way rather than add a 3 mm spacer under the cylinder.

 

[fatcaaat]

For those of you with Honda nice engines. You will also come to realize that some parts are now becoming harder and harder to get. One such example is the clutch basket is bespoke to a Honda. Nice. The good news is that the new Honda TRX 90 baskets Can be swapped in with just a tiny bit of adjustment if you have a lathe. In the US these clutch baskets cost approximately $130. When you order them from China they only cost $40 shipped. Unfortunately, when they ship from China, they can also become damaged as you see in this picture. The vendor told me that it is perfectly fine to run it this way and refused to help me. I filed a complete with PayPal and we will see what happens. This is an actual Honda part made in China.

 

[fatcaaat]

I have previously attempted to use a TRX 90 countershaft to replace a completely worn out Honda nice countershaft and it resulted in no third gear. After some careful measurement in cutting in the lathe , I am pleased to report that a TRX 90 countershaft can in fact be used. Why is that important? It’s really only important if you plan on putting 30,000 miles plus on your engine and never swapping your front sprocket when it begins to wear out. It really only matters when you purchase on a nice core engines that are completely clapped out. A replacement Honda nice counter shaft will set you back about $80 plus shipping from a foreign land. A brand new TRX 90 shaft run runs around $40 stateside and requires 15 minutes in the lathe. Your choice.

 

[fatcaaat]

The crank is now together and ready to go. I built two cranks with stroker pins. Unfortunately, one of them only had .001" interference fit on the pin to crank on the flywheel side. A little weld will keep that nice and secure. Both of them are within .002 runout so better than honda specification. waiting on the cylinders and pistons now. I did not do the assembly work on these as I was too nervous about assembling a stroker pin so these were farmed out to a guy in PA that I trust.

 

[fatcaaat]

56mm setup (and54too). I had a set of both made to my specs because theres not any good options to have them done at reasonable cost and high quality. I have a limited number extra available if anyone is interested. Assembly may now commence.

 

[fatcaaat]

I got a lot of the build done today so here's some updates. Going to add pictures via my phone...so first the text.

In order for the crankshaft to clear, I had to grind out a bit of the inside turbulance webbing on the cases. The good news is that it only needed to be relieved and not actually removed like on my 66mm crank. I could have chucked this up in the CNC and programmed a path but honestly, I just used a die grinder and then sand rolled it. It came out perfectly fine. For you shadetree mechanics, NEVER EVER use a die grinder for your cylinder bores...back in the olden days when I didn't have equipment I was as surgically precise as I could possiblly be with a die grinder on the cylinder bores and while you can get away with that up to 54mm if you are very careful, you have to have the precision of machine tools to go beyond 54. Been there, done that.

 

[fatcaaat]

The rest of this was generally standard assembly. For those keeping score, I am running the stock camshaft on this build. You might be asking why i'd do this...well, two reasons. First, I have a stock cam, so it makes a lot of sense. Secondly, I am likely to build another one of these from a core I have sitting here, and that one will be done a little different and a little more excessive. I already have the cam and the piston will need to have the pockets deepened. But other than that, pretty straightforward. I am stuck in that I do not have the slinger gasket or the cam tensioner assembly...the ones I have are no good.

 

[fatcaaat]

Here's why you inspect everything. Look at this picture. Hairline crack on the shift detent arm. Yes, I have spares.

 

[fatcaaat]

These clutch springs are the best clutch springs I have ever used across all builds...chinese big 192cc builds all the way down to stock honda nice 110. These are stainless and absolutely amazing. I get them TRP over in Germany. They refuse to tell me what the original application for them is, or maybe they are something they had done up. I dont know. But I gladly peel off a Jackson $20 for a set. Every motor I have has a set of these in it. I simply don't use anything else.

 

[fatcaaat]

I am electing to use the full size sling on this build. Its bot going to be revved beyond 8k and will be really smooth across the whole bandwidth with that 61.5 mm crank and mild cam

 

[fatcaaat]

So this is now pretty much done. I have to repair the neutral pickup and replace the plastic plugs and clutch protector but that won’t impact anything. I have a vm20 on top and i know thats going to be too small for optimal performance but thats what i have so thats what im going to start with. This will probably be good for 65-70 mph properly geared and will make good power across the whole bandwidth. It is going to start life in a cl70 clone called nostalgia 50cc. What a turd. But i think it will be my go forward test pig.

 

[fatcaaat]

56 bore and 61.5 stroke makes 151cc. It will probably need an oil cooler. So thats will be the next update along with it being mounted and possibly running. The nostalgia 50 exhaust is going to be restrictive even if i cut it open since the header is small. I’ll probably have to make something

 

[OLD CT]

Hopefully you won't get intake icing with that plastic spacer. They always made it difficult for me to jet/tune the carb on a build that rolls along at 50+. I would hear gurgling, and the intake would get water droplets all over, condensation in the spring. Maybe they are good on a z50 that's ridden at very slow speeds in the woods. I seem to remember a z50 had the spacer in that spot from Honda. I usually see around 130 degrees intake temps, that's good for more complete fuel atomization. Hot rod v8s like cold intakes, Honda singles like a little heat.