Another custom nice engine

fatcaaat

Well-Known Member
Thanks! Few things that need to be completed here. I'm going to be putting on some better levers and perches...billet items instead of these. Did you notice the front end is a Dual Disc setup? I'll also be fabricating a rear rack and short sissybar. I'm also going to change out the bars as the lower loop doesn't fit correctly between the clamps, so I'm going to fabricate my own bars.
 

fatcaaat

Well-Known Member
So we're making progress. Today I got the carb in the mail. PWK26, got it all mounted up and started with 45/100 jetting. One kick and it started...and I could hardly believe it. Then oil pouring all over the garage floor from the head. Turns out I forgot to do two things...1. actually tighten the oil take off bolts...but more importantly, did not cut holes in the gasket so oil could divert through the cooler. issue 1 actually saved everything because if it had not leaked so bad, I might have just let it go and not realized oil wouldn'be be circulating to the head. I would have figured it out in a min when the cooler lines were not heating up, but happy it went down' this way.

A few things were surprising to me, besides the fact it started on the first kick and actually idled. For starters, usually when you remove all that rotating mass, you have to make the bike idle much higher, say 2000 rpm. That does not appear to be the case here. It seemed to idle ok around 1500. Now granted it's currently quite rich at idle and I need to get in there and swap that pilot. but other motors i've done with lightened flywheels and nothing else on the crank don't behave this way. That was a pleasant surprise. The other surprising item is how it sounds. Just by how it sounds, I can tell that this motor is going to be something radical. I had a Honda Nice 127cc with a takegawa 4v+r head on it. I did not touch the head and just mounted it as it came in the box. That motor topped out just about 70mph. I can tell, right now, that this motor will be faster than that one, even without riding it yet.

Before i jump the gun on the head and cylinder combo's, i'm going to ride this before I put a verdict in. If i find that I really like this setup, I will likely purchase a 56mm bore setup and put it on top of the current 142cc Nice I have sitting on the shelf, making it a 4v 152cc.
 

fatcaaat

Well-Known Member
Got a chance to ride it around the neighborhood today. It pulls like a train...wow! And with the rotating mass at a minimal, it accelerates very very very quickly. The jetting is pretty close but still have some work to do. It seems to idle pretty well around 1500-1700 rpm which is about right for this setup.

Three shakedown issues to resolve...first, I cannot get the dual caliper setup bled out. So i have very little front brake. Second, the front end is way too soft so I'll have to maybe add some preload pucks and some heavier oil. Third, ironically, is no third gear. First, neutral, second, neutral, fourth. Well, not exactly, It will go into third, sometimes. Behaves almost like the detent arm is off the star. I'll have to investigate. I know for a fact that it bench shifted and I cannot imagine I put it together incorrectly..even if you miss a spacer, you still get all the gears. I sure hope to hell i don't have to take it back down to cases!
 

kirrbby

Well-Known Member
Well you must have kicked it over at least a few times now...how does it feel...ok?
I'm sure you left the oil lines loose because you hadn't cut the gasket yet. So...not really a mistake there.


Got a chance to ride it around the neighborhood today. It pulls like a train...wow! And with the rotating mass at a minimal, it accelerates very very very quickly. The jetting is pretty close but still have some work to do. It seems to idle pretty well around 1500-1700 rpm which is about right for this setup.
This is pretty awesome. Well...except for the 3rd gear thing. Hopefully the cure is under that clutch cover.
I'm excited to see how this one turns out.
Interested to see how well you end up liking the lightened crank assembly. That might be a really good modification for the stock, or BB Nice engine...to add a little zip. Maybe remove a little weight...then see if you want to take a little more. I should look into finding a used Nice, flywheel and oil spinner to use for that.
 

fatcaaat

Well-Known Member
Well you must have kicked it over at least a few times now...how does it feel...ok?
I'm sure you left the oil lines loose because you hadn't cut the gasket yet. So...not really a mistake there.



This is pretty awesome. Well...except for the 3rd gear thing. Hopefully the cure is under that clutch cover.
I'm excited to see how this one turns out.
Interested to see how well you end up liking the lightened crank assembly. That might be a really good modification for the stock, or BB Nice engine...to add a little zip. Maybe remove a little weight...then see if you want to take a little more. I should look into finding a used Nice, flywheel and oil spinner to use for that.
No need to find a used oil sling, as you can find the chinese ones either already lightened, full size, or even aluminum ones. That's an easy and cheap way. Then mod from there. Flywheels will be near impossible, so another option is to just use a replacement, normal, setup under the cover and mod that. Same thing...cheap and modify as you need. I buy these: https://www.ebay.com/itm/133305750784 which are setup the same way as the 1991-94 CT70 and the nice as far as wiring is concerned. I put these flywheels on everything I have that is not honda Nice, but I think one of them actually has this on it. I also just installed 4 of these on my buddy's bikes because he was running 4 different types of ignitions on them and always had trouble starting them. Now his bikes start right up.

The false neutral in third is disappointing and I do hope it's as easy as something under the clutch cover.

BTW, i've emailed Yumanashi to see if they will sell just the 56mm piston and cylinder setups but they have not responded. I think I would put one on top of my 142 stock head nice and turn it to a 152 4v and mate it with a PWK28 carb.
 

kirrbby

Well-Known Member
After replacing the broken kickstart pinion and 1st gear (actually swapped out the whole transmission) on my son's 124cc trx90 engine... it was...kinda, jumping a dog maybe, in third gear, when under power. Felt like it would pop out of gear for a half second, over and over. ...anyways...when I went in, expecting to find worn gear dogs that I had overlooked...everything looked good. Except, it was missing the thrust washer on the right end of the countershaft. I was surprised that the thickness of that washer was enough to allow it to pop out of gear.

A 28mm carb sounds crazy big. But I guess so does 152cc...and two 19mm intake valves...
 

fatcaaat

Well-Known Member
I do think i'm going to pop a VM26-606 on this engine. I have the PWK26 on it right now. These are actually used on 2 strokes. D-slide type carbs. the bike will idle fine, and also seems to do pretty well across the rev range, but my experience on two of them is that they load up at idle. I have another motor running one and if you let it idle for longer than 30 seconds, when you go to take off or blip the throttle you can tell it is loading up. I'm not sure why that is happening. Perhaps, I need to drop the pilot jetting even further, even though it seems to idle just fine and get the idle mixture screw as lean as possible at 1-1.5 turns. I wonder if 2 stroke engines just need fatter idle jetting and are calibrated differently? I don't have any experience with them.

Anyone on here can add insight about direct compares for idle jetting for two-vs-4 stroke engines? The question being simply "for a particular jet in a carb, let's say 38 sized pilot, would a 125cc two stroke require more, less, or same amount of fuel at idle? Or would a 2 vs 4 stroke engine have a stronger vacuum pulling mixture into the combustion chamber?
 

fatcaaat

Well-Known Member
Well, it's all back together now...what a PIA. I thought that this bike setup with the rearsets was going to create the ability for easy enging swaps...that was the whole point of the way I set this "shop bike" up. But turns out it is as or more complicated to remove an engine becaues the rear sets are mounted to the lower engine mount, and hence every time you want to take an engine out, you have to completely remove the rearsets, and rear brake setup. I digress..

I took the motor down to parts, and gave it a good examination. Glad I did. the cam chain was chewing into the top portion of the engine cases because the cam chain setup and conversion from Nice 32/16 to 28/14 and different combinations of rollers. I ground a little bit of relief and that should keep the fairy dust out of my engine oil.

For those keeping score (and more importantly, those that have honda nice engines) you CANNOT swap the counter shaft of a TRX90 in with a Nice 110 counter shaft...they are really close, but not the same. you CAN swap an entire gear stack that includes the drum if you need to. I was very careful in my measurements and assumed that the 1mm positioning difference of one of the notches could be shimmed out. Not the case. Now, that I know what's what, I could chuck that TRX90 counter shaft in my lathe and reposition the notch and it would work. So, that's a project for another day to make that happen and then put it away with a label so I remember. The likelihood of a countershaft being bad is extremely low anyway but the engine I got from thailand probably had 50k miles on it with a loose sprocket, which chewed the end up really bad. I suppose the answer will be for me to weld it up and recut the splines...i'll do that if I ever get desperate for one.
 

fatcaaat

Well-Known Member
keeping things straight for you, on the reassembly I did something a little different. I don't think it matters at the end of the day, but maybe it does. First time, I used two base gaskets sandwiched between 2 0.4mm aluminum base gaskets (spacers). That brought the piston to TDC and perhaps just a tiny bit proud...only enough to catch your fingernail. And because of that, I used a thick 0.75mm cometec base gasket. This time, on reassembly, i used two base gaskets and a 1.2mm aluminum spacer, and the piston was in the hole enough to catch a fingernail. So, I was able to use a thin copper head gasket that was only 0.25mm thick...that means that I've effectively raised the CR a tad bit as I suspect I've reduce the combustion chamber volume. I would assume that would provide me a little more power...might not be noticible.

The bike is still being setup and dialed in...this week I'll receive different handlebars, i have to relocate the brake diverter valve, I'm swapping out the headlight assembly, and still have to get the brakes bled more effectively. I've always had great success using speed bleeder valves in my brakes and if I cannot get it next time I try, i'll order a set of those and I'm sure I'll be able to complete the task quickly.

Lastly, because I am removing the original style headlight and speedo, this bike no longer has a speedo on it. So I need to come up with a solution for that. Not sure what I'm going to do there, but it will not be a cable driven speedo. I can go with a GPS or a magnetic one...but whatever I use will need to work in a batteryless setup, so it has to be something that does not use a lot of power. I guess if I ever needed to pop a battery in this I can, but I wired in a large capacitor instead and that seems to operate everything just fine right now.
 

kirrbby

Well-Known Member
If I'm reading this right...I'm a little surprised that you wanted MORE compression on this engine, given the hard to kick situation. Must be OK?

I've always wondered about the GPS speedos...Do you have to pay for GPS service? I assume not.
 

fatcaaat

Well-Known Member
If I'm reading this right...I'm a little surprised that you wanted MORE compression on this engine, given the hard to kick situation. Must be OK?

I've always wondered about the GPS speedos...Do you have to pay for GPS service? I assume not.
Kicking it over wasn't a problem...you get it to TDC slowly with pressure and then you give it a nice hard kick...no issues getting it started. Just don't stall it at a red light because you have to do that process every time you kick it, and that can take up to 20-25 seconds which will feel like forever when people are honking at you.

I've had a GPS speedometer on a motoped bike and it worked pretty well when you had good clear access to the sky. On my property, that's not the case, but once you get out and running, they seemed to work fairly well. No subscription needed. My phone could work for this application, but the bike needs a speedometer in Virginia.
 

fatcaaat

Well-Known Member
Alright here is a good update for all those following along. I have a speedo/tach combo on it now, along with a mikuni vm26-606 carb. I got to take it out for a 25 mile test run today and this is what I have with it.

It is currently geared the same as my Stock Nice engines at 18/33 with same size 110/90-10 tires or actual 4.0x10 tires. Obviously the engine dynamics are very different given that it has no oil sling and a light flywheel and a porkchopped crank. That said, it's fast for a 124cc. I have not done anything for extended periods, but it gets to 65mph pretty easily. I did not try top speed runs. Comparatively, 65 is the absolute maximum the stock engine will run.

You have to clutch it a little bit off idle, which was expected. once in first, if you snap the throttle, it will do a power wheelie. The stock Nice will not do that. this engine likes to be higher in the RPMs, and I would consider it lugging at 4000. A stock nice you can take down to 2500. I also find myself shifting this engine in the 6500-7k range and once broken in I could see myself taking it up to 8-8500 regularly. I simply do not do that with a stock nice.

There are some things that need to be corrected still. I think my first run was jetted lean and the engine was a lot hotter than expected. I have upped the main jet 3 half sizes from 160 to 175...mostly because I don' t have any 165's or 170's. I'll add those to my list. The cam chain loosened up and I heard it slapping around. I went in and had to modify the tensioner rocker so it had a little more movement. I'm also near certain that the exhaust is restricting this motor. This is a custom bent supertrapp replica made from 1.0 OD and transitions to 1.5. I think I need to bend up a 1.25 OD version but I don't have a 1.25 die. The original Supertrapps are made from 1.25. Lastly, the clutch is slipping on hard acceleration 1-3 gears. Did not notice it slipping in 4th. So, I'm going to need some heavier springs. I was concerned about this at the beginning and am surprised that the stock Nice springs don't hold it. Since I'm running a trx90 basket, i'll use TRX90 heavy springs.
 

kirrbby

Well-Known Member
Good progress. But you still have work to do. This one's gonna make you work for it.
That cam chain issue...seems like a problem. Do you have a fix in mind.
I remember seeing a cam chain master link available somewhere before.

I see you using those tb style oil coolers often enough. You must be flipping the mounts on them so you can feed them from the top?

What is the purpose of the pork chopped crank? Is that just to reduce weight? Or is there another reason for that.
 

fatcaaat

Well-Known Member
Good progress. But you still have work to do. This one's gonna make you work for it.
That cam chain issue...seems like a problem. Do you have a fix in mind.
I remember seeing a cam chain master link available somewhere before.

I see you using those tb style oil coolers often enough. You must be flipping the mounts on them so you can feed them from the top?

What is the purpose of the pork chopped crank? Is that just to reduce weight? Or is there another reason for that.
They porkchop them to lighten them and balace them.

This bike runs an earls performance cooler. Most of mine do. One has a tb version, one a takegawa. Yea easy enough to flip the mounts.
 

fatcaaat

Well-Known Member
Waiting on a new throttle cable so i made some bars.
 

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kirrbby

Well-Known Member
Very cool fatcaaat! Don't think I've ever seen any others like that.
They're going to look really good on there.

I've heard of "earls" many times in discussion about cooler lines and fittings...but never knew what earls meant. And didn't even know of their line of oil coolers.
 
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