Another custom nice engine

Im getting into these customs and wanted to do something very different.

Follow along. This motor is destined for my rat/shop bike which will be on the street in sleeper mode.

Started with a honda nice 110. Must have been the dirtiest motor internally I’ve ever worked on. Took about 4 hrs to clean it and another to inspect it all. This was the second core I recently received. Other than the counter shaft being shot it met spec everywhere. Kirby set me up with a trx90 shaft and im in business.

I bored the cases out big...why? in case in the future I want to go big. I bored the cases to 58.5mm so i can easily run a 56mm. I have to offset the bore if I want to go to 57 or 58mm so this is the largest you can go before the offset.

Now the custom. I wanted to use the new 54mm kitaco crank and matching nikasil cylinder i had so needed trx90 studs. The crank is completely different so I purchased a cd70 crank gear and takegawa mini sling setup. The nice crank has a pin and gear for the oil pump, a gear with key for the clutch drive, and a long splined section for the oil sling. The takegawa crank is the normal style like CT70's have, so lots of fun working that out.

I now needed to move the clutch basket in about 6mm so had to reslot the main shaft and shim it out. Then i dropped the nice 110 basket and broke it. Got a trx90 setup from ebay and got back to work. The TRX90 and Nice clutch basket are not identical...the nice is a superior product in all senses, but a TRX90 will work if you can machine bushings or bore the center hole to match the Nice dimensions. I made a bushing and left the basket alone. Then the throwout bearing was in too far because i moved the clutch in so i made a custom throwout.

Lastly which i will update when its installed is a yuminashi 4v head. So ill have a mostly nice bottom, mated to a kitaco crank, takegawa crank gear, trx90 basket, kitaco cylinder, and 4v head.

Lastly i took 12oz off the stock nice flywheel. I'm going to steal the 22mjn carb from my 142 nice on the shelf and its done.

Wow! That's a lot of trickery in there.
You must have needed to move the clutch inward because of the crank swap? To get the primary gears lined up properly?

Is that mini oil sling designed, and sold, for the Nice 110 engine?? Or a different engine? Made for a guy who wants to lighten up the crank assembly/flywheel?

I like the idea of shortening the stroke of the Nice engine. Shorter stroke, bigger bore, "square" engine at 124cc.
What do you think of the 136cc setup for a Nice 110? That would be VERY close to square also...and 12 more CC's. Would it behave similarly to the 54x54??

I think it's doubtful you'd notice much of a difference between the 54mm kitaco crank vs the 55.5 nice crank anywhere. The main reason for the swap was because I had new Kitaco parts laying around and I wanted to have some nice spares for my fleet of nice motors. And, curiosity got the best of me I suppose...could it be done? yes is the answer.

To answer a few questions...yes, i had to move the clutch inward because the crank gears needed to line up and the mini sling was encroaching on the basket. The mini oil sling is for the CD70-90. I had to make a pressed in tube from the clutch cover to extend into the sling as it was too short to reach...no big deal, and honestly is better than the stock design IMO. the cd70 has the clutch on the primary shaft and not the crank...i always wanted to get my hands on one of those motors.

I hadn't considered putting the 56mm setup on top the nice due to past experience of my problems with head gaskets and base gaskets on 56 and 57mm bores on these small block stud spacings. However, that was prior to me having a real shop with real equipment...so boring the cases with the right equipment eliminates that concern. a 138 using the stock crank is probably pretty badass. I could see a future where I get one and install it and it woudl make a little more power.

I just got the thai-based parts a few min ago...going to open them up and see what's what.

I'm definitely interested in your opinion of that kit. I have monies set aside for one if you think I could trust that head. I wouldn't want to risk a good lower end, if the quality is questionable.
I'd probably go for the 56mm kit.

Pain to assemble the head. The piston sticks out 1.5mm with a 69mm tall cylinder. Forgot the connecting rod length is 1mm longer than the taky 54mm crank. I have a 1mm alum spacer sandwich between two gaskets should do it.

Ok this thing was tough but its mocked. It would be done if i had the right length cam chain. 84 for a 69mm cylinder normally but going to need an 86.

it's probably not going to run for a couple of weeks just based on schedule but there's a few things that caught my eye and I'm not sure yet what to think about it. Kirby, if you end up getting one, we should chat before you attempt to assemble the head. I can save you some headaches.

Quality wise, I think it seems like a pretty good quality item. Is it honda? No...but it seems better than many china parts I've had in the past. The intake track and exhaust tracks seem unreasonably large. Not just a little large...HUGE. and based on that, my idea of using a 22mm carb is going to be out...thinking i'm going to need a 26-28mm and rev the hell out of the motor...that's ok, that's what I planned to do anyway, but it seems beyond crazy. The cylinder isn't a standard Nice length nor a standard 69 length...it's 73mm and they supply you with a spacer and some extra gaskets to get it where it needs to be to use a standard crank. That stuff is fine and parts are well made.

I was planning on taking the second head and putting it on my 54x62 stroker engine, but based on what I see, that would be a waste unless I pop a 57mm bore on there. with it being so undersquare, it won't do what I want with that big head on there, so i'll hold it for the future or another project.

I suspect it will need an oil cooler...but it's not setup to accomodate one. And to put one on, it will need some tom foolery. Not impossible, but not straightforward either. If I feel inclined, i'll program them and mill them out on the CNC.

Cant buy an oil cooler takeoff for these so i made my own.

You make it look easy...I know that it's not. Had to grin when I read back..."this one was tough". lol
86 cam chain? Is that just because of the shim under the cylinder? The TRX90 studs were still long enough tho...just 1mm or so less, sticking out?

I thought those ports sounded pretty big in the sales video...and I think they said 2-19mm intake valves..? That's pretty big. I hadn't considered...maybe TOO big.

kirrbby said:

You make it look easy...I know that it's not. Had to grin when I read back..."this one was tough". lol
86 cam chain? Is that just because of the shim under the cylinder? The TRX90 studs were still long enough tho...just 1mm or so less, sticking out?

I thought those ports sounded pretty big in the sales video...and I think they said 2-19mm intake valves..? That's pretty big. I hadn't considered...maybe TOO big.

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i don't know why it's 86 chain...i think the head is potentially taller than stock and when you change out the gearing from 32/16 to 28/14 something seems to get lost in translation. either way, 86 should work just fine. It's not just the extra 1.2mm shimming plus 2 base gaskets making it need 2 more links...

The trx90 studs were fine though. But again, if you are putting this on top of a Nice, you won't need the studs...use the stock nice studs and the stock nice cam chain with this setup if using the stock crank. trust me it's a BIG job to retrofit a normal crank in here. I never would have attempted it if I didn't have the Kitaco parts. It should be an amazing engine that will pull to the moon.

Don't forget the plugs. no specs, no instructions come with the head so some of it is trial and error. Plugs are not standard size. you're going to need more reach.

NGK 4218 CR8EIX Iridium IX Spark Plug​

I keep looking back at the video for that kit.

I wondered about the spark plug at one point. I thought I'd seen a typical NGK CR7.. .ct70 plug for sale on their webpage...so I thought the kit might use that plug. My modern works 4v head uses a tiny iridium plug...m8...tiny threaded hole in the aluminum head...makes me nervous each time I tighten the plug.

I understand now with the cam chain...you've changed everything up...both gears, etc.

Couldn't you still run the 22mm carb? Can't get enough air thru it I assume? Worried it might whistle??lol
I figure it would WORK...but it would just be too small and hold back the engines potential...top end mostly..?

a 22mm carb would certainly run the bike, but not to it's potential. It would really depend on what I use it for and how I plan on riding it. The bike it is going in will be well setup...suspension, brakes, etc so there will be no limitations on the chassis. My three other CT's are all setup for touring...take them out for 200mile+ days (just did a 250 mile day last weekend). I don't need another one of those, so this bike will be setup to thrash and that being said, i want it to wind out...so it will be geared appropriately, and revved out all the time. The other motors never really see much above 6500rpm...just don't ride them that way.

I would suspect that the motor will be optimized with a 26/28mm carb to have it reach it's potential at the upper RPM ranges. I also expect it's going to be rather terrible off throttle and underwhelming under 5k simply because of the engine setup...very low flywheel effect and head that is setup to operate in higher rev ranges. I will be the sweet spot for this motor will be between 6500-9500, which should be OK on this engine. Whether or not I like it is another thing.

Flywheel effect means...the weight of the flywheel helps push the engine when between revs?? So the lightened flywheel and oil sling will require you to stay on the throttle...so the piston has to do more of the work?
But the lightened flywheel also helps to ALLOW the piston to do the work...quicker...better response?

kirrbby said:

Flywheel effect means...the weight of the flywheel helps push the engine when between revs?? So the lightened flywheel and oil sling will require you to stay on the throttle...so the piston has to do more of the work?
But the lightened flywheel also helps to ALLOW the piston to do the work...quicker...better response?

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Yeah. Large rotaining mass like a big flywheel and big oil sling take some power to get moving...it also smoothes out power delivery and idle on a small engine. The more mass you remove, the faster it will respond to throttle input, but means that you will be on the clutch more during takeoff, the engine will come down from revs faster (particularly when pulling in the clutch to shift) and also result in less engine braking, albiet only slightly. They generally accelerate a lot faster and respond to throttle input much faster the lighter you go. They can also become really easy to stall. One thing for certain, is that a motor that is not tuned correctly will be a lot less forgiving without that rotating mass.

latest development...I ended up using an 88t chain. that was incredibly surprising to me. there simply was no way i was going to get the 86 to make it. to make the 88 work, I had to slightly increase cam chain tension. I also added a slightly thicker head gasket which should take the CR down about 1/2 point which I'm perfectly fine with.

I installed it in the bike and WOW am I concerned about kicking it. The Honda Nice has the beefiest set of kicker and first gears on any of these lay down motors, and I have to say i'm even a bit concerned, even getting it to TDC and giving it a full kick is work. Hope I don't stall this at a redlight. Sometimes they do loosen up.

Next up is to figure out how to mount the oil cooler. I'm waiting for my carb, which will be a PWK28, the same type that Kitaco uses for their own dyno pulls.

Kicks over easily if you pull the spark plug tho?
No way to add some sort of compression release?
I hate that...cross your fingers...kickstart. It's a bad feeling.

kirrbby said:

Kicks over easily if you pull the spark plug tho?
No way to add some sort of compression release?
I hate that...cross your fingers...kickstart. It's a bad feeling

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There is no binding, but it doesn't kick over that easy to be honest. The spring tension for the 4v is pretty high, and the cam is very lumpy so it takes a lot of inertia to get it up and over those cam lobes. So even with the plug pulled it doesn't just roll over by hand...you have to give it some muscle. It will be fine I'm sure, but i'm starting to get excited for what this motor might be. I have built a Nice 127 previously with a 4v superhead and another member of this forum owns it now. I thought that this motor would be very similar to that one, but now I'm starting to think this will be an entirely different beast.

Installed and waiting on the carb.

That bike is awesome fatcaaat. I LOVE that thing.