Stinger MKII Rebuild

[Bakauata]

I have had my Kyosho Stinger MKII stripped down to the last screw for a few weeks now. I needed shock oil, and diff grease before I could start to rebuild.
The car has had quite some use and It took me quite a lot of work just to get the parts moderately clean.
Unfortunately, after having worked on the thing for a while now, I've come to realize the O.S. CZ-2 engine has no compression. After a suggestion from the guy at a local hobby shop, I pulled the piston and sleeve from the engine and confirmed the piston goes right through. Bummer. I didn't want to spend any more money on this, but I may have to buy a new engine. There's a NIB O.S. 15 CV-X with recoil pull start on sale locally for approx U$190. It would be a direct drop-in.

Original belt is disintegrating and tires are flat on the side they sat on for years (as well as cracking). Luckily I had the foresight 30 years ago to buy a new set of tires and belt. I had also added ball bearings and Gold shocks back in the day. Lost the wing unfortunately.

I'm planning on using a thirty year old Tamiya Molybdenum Grease, which I found with my old kit, in the differentials. Anything I should be aware of?

Hera are some photos (of a load of parts!)

[TheDiamondOne]

Nice build, i will be watching. That grease is fine, actually any automotive grease is fine in the diff. U can get that sleave repinched for about $25. Need to stay with that engine! Rayaracing - Resizing Service & Equipment
http://rayaracing.com/

[Bakauata]

So I've started rebuilding. I filled the shocks (Kyosho Gold) with a generic silicone oil and closed the cap, but the piston seems to already have some bounce back, even without the spring. Is this normal? I followed the exact procedure from the Turbo Optima manual, which has these same shocks. I imagine it's the air behind the diaphragm in the cap getting compressed, but I was expecting the piston to stay in the pressed down position .

[coxbros1]

You have rebound in the shocks. Pretty normal on kyosho golds and bladder shocks. There is fine line between rebound/air in the shock. It can be done tho. Just takes patience.

[Coelacanth]

One possibility is you might have just a tad too much oil in the shock body. What I do is fill up the body with just a bit too much oil, then when you press down on the rubber diaphragm, it squishes out the extra oil...wipe it up and screw the cap on. That usually gets it right, but if it still decompresses on its own, squish out just a bit more oil and repeat. Other factors that could cause the self-decompression are too heavy an oil weight for the piston rings you've selected, or the piston rings chosen have too small holes. Going to a lighter viscosity oil, or choosing the red piston rings with bigger/more holes will let them compress & decompress more easily.

Like coxbros said, it's a bit of a balancing act for the shock feel you're aiming for, but with practice you'll get it sorted out.

I went through all of this dialing in a set of 3Racing shocks for the Lazer ZX-5 to make them work for the Optima. They came with a too heavy oil and pistons with too small holes, at least for the Optima. Once I put in lighter oil and opened up the piston holes a bit, I got them working just as smoothly as the Kyosho Golds.

[Bakauata]

Thanks guys. Looked up “rebound” after getting the tip from coxbros and found a few videos on the subject. So rebound is actually normal. I fiddled with the shocks until I got them all not too bouncy and roughly equal.

Here are a few progress shots of the rebuild:

Rear tansmission. Teeth are in pretty good shape.

Front diff. Note the belt is narrower than the splines on the diff. This belt is likely not the exact replacement. Maybe an Optima spare. Not sure.

Wheel assembly includes tire, plastic insert, two piece wheel and 4 screws. These arn’t the original tires. I remember buying these because they were the closest ones available at my LHS.

First part done:

[keithrc]

Nice thread, I don't mind the Stinger MK2 and wouldn't mind getting one one day. Are they difficult to find these days? I've been looking for English instruction manuals but so far haven't found any, only the Japanese versions. Finally, did these come with the CZ2 or CZR engine?


Keith

[Bakauata]

Nice thread, I don't mind the Stinger MK2 and wouldn't mind getting one one day. Are they difficult to find these days? I've been looking for English instruction manuals but so far haven't found any, only the Japanese versions. Finally, did these come with the CZ2 or CZR engine?


Keith

Thanks.

I posted the English manual just a couple of days ago. It’s uploaded to retromodelisme.com. Here’s the link to my post in this forum:
https://www.rc10talk.com/viewtopic.php?f=82&t=43877

I bought mine with an O.S. CZ-2 back in the 80s.

I’m not sure how hard they are to find. Everything is hard to find where I live. I don’t see any on eBay at the moment, but I have on occasion. There’s a Turbo Burns ending in a day though.

Regarding the manual, I noticed an inconsistency (maybe a Japanese quirk) while assembling the front drive train yesterday: It emphasizes you should assemble left hub with right knuckle arm and vice versa. Both knuckle arms look identical (other than the markings), so I went ahead and did what the manual says. But it defeats all logic.

[Bakauata]

Continuing with the manual critique, I came across a couple other issues:

1) The car came with a transparent plastic belt guard/cover which ran along the base plate from the rear to the front diff. It was held down with a couple of braces. However, (other than I lost the guard/cover long ago) there is no mention of these parts in the manual. It might have been a later addition, and I may have lost the manual errata.

2) The other thing is, there is a connecting rod which connects the rear bulkhead to the top plate. The manual indicates a reference length for the rod, but when I pressed it into place, the spur and piñon jammed up. There are three adjustments which affect this: The rod length, the front diff position (which can be slid for-aft to adjust belt tension, and the engine mounting which can also be slid back and forth. The manual does nos mention in which order one should adjust each of these. Nor does it mention how much tension the connecting rod should exert.

Well, thought I would document this in case anyone comes looking.

[coxbros1]

I like how those engines sit at an angle, looks tits!
Also, how do u get those red arrows like that?

[Bakauata]

I like how those engines sit at an angle, looks tits!
Also, how do u get those red arrows like that?

Yeah, the motor mounts are angled at the base. I suppose it's meant to expose the heat sink forwards.

I put the arrows in in Photoshop. I can show you how it's done if you have access to the software.

[Bakauata]

Here are some pics of the fully built model (minus electronics and fuel tank):

Have the box too.

[XLR8]

Hey that's a very nice restoration. Well done!!
Thanks to your posts, I know what a Stinger is - it's basically a nitro powered Optima Mid (or perhaps an Optima Mid is just an electric powered Stinger?). Either way, it's a very cool car. Are you planning to run her?

[Bakauata]

Hey that's a very nice restoration. Well done!!
Thanks to your posts, I know what a Stinger is - it's basically a nitro powered Optima Mid (or perhaps an Optima Mid is just an electric powered Stinger?). Either way, it's a very cool car. Are you planning to run her?

Thank you and You’re welcome. After looking through the kyosho prefix list on this forum, I now know that about one third of the parts listed in the manual are Optima parts. The Optima re-releases may breath new life into the Stingers requireing spares. Thankfully mine has nothing crucial broken or missing. I do plan on getting it running, even if I won’t run it much. But the engine is toast, so I’m looking into my options. Buying a replacement, although not the same as the original, is my best option for now.

[keithrc]

Love your work mate, thanks for the link to the manual. That'll be very handy for those of us looking to have a Stinger in the future. I thought a lot of the parts looked very Optima-ish.


Keith