Taiyo Juki Bobcat repair

[jirushi]

Hi,

Last Sunday was a good day: I picked up two parcels containing many airgun related goodies from the USA.

These two Taiyo Juki Bobcats needed to be resealed. Normally I would send the valves to Lawrie aka "The King of Seals", but these turned out to be very easy.
The stems screw into the brass head, which is great. Terry Robb's QB78 valve seals fit like a glove, and seal well. Then I used Crosman 160 seals from Ped's kit. The probe o-rings came from my collection of old o-rings. I have only tested the .177, a big bang and three shots at 194, 195, 194 m/s; about 640 ft/s > 7.7 ft/lbs (8.44 gr JSB's). Must do a full shot string, it might be very steep. The tube holds 2 powerlets, of which only one is pierced; the tube cap does not have a piercer. The second is probably meant as a spare, for hunting situations? Japan only made airguns for competitions and hunting.
Very little is known about Taiyo Juki. They made a few models, of which the Bobcat, 380, Junior and Grand Slam are the most common. I think they were sold in the USA, New Zealand and Japan. There is also a Deluxe, which has a magazine. All work on CO2; I don't know why they didn't make pumpers, as those were very popular around that time (the seventies). I have read that Taiyo Juki's were made by the well-known firearms manufacturer Miroku. Miroku did not answer my email for more info (I didn't expect a reply, but ya never know!).

There is some info on the net. A BB Pelletier report
https://www.pyramydair.com/blog/2009/09/taiyo-juki/

Great info on the Grant the Kiwis forum (New Zealand). Grant has two boxed Bobcats. Also info on Danny's forum of course.
https://www.tapatalk.com/groups/gran...isairgunforum/

A great Junior repair report (Another Airgun Blog, such a great website)
http://anotherairgunblog.blogspot.co...h?q=taiyo+juki

A Baker Airguns ad
https://www.bakerairguns.com/product...-pellet-rifle/

These reseals were nice and easy. Now I need to do some testing.
The .22 (top) was very kindly given to me by a member on here from Virginia.
The .177 I found on Gunbroker, and a friend and fellow Titan fan in the USA helped me to get it. It was cheap. The action has a paint finish. I think it is not original. In fact many parts on this example are not original (open sights, screws, trigger spring). But that don't matter.



It is a Crosman 160 clone (yes, I wear awful slippers when tinkering):



This one had miles of trigger creep. I glued some leather on the trigger to reduce sears engagement. Much better now


These old seals become like a sort of tar


Valve stem disassembly. The valve return spring at the top left is not original. It should be longer. I fitted a few washers to make it work better.


Thank you "The Robber" (not everyone likes him lol!)


This German Haweka sight has great glass. The loading of the .177 pellets is a bit awkward with this low mount though.


Any fellow Taiyo Juki owners on here?
Cheers, Louis

[lightning22]

I’ve never heard of this Louis, trigger unit aside it looks very much like a QB from what I can see. I assume better quality components?

[Geezer]

Uitstekend!

[Mark D]

Nice write up Louis

That looks so like a Cr 160 when taken down - I guess suing companies for patent infringements was a lot harder back then.

Was the Cr160 design ever patented ?

[45flint]

Nice write up Louis

That looks so like a Cr 160 when taken down - I guess suing companies for patent infringements was a lot harder back then.

Was the Cr160 design ever patented ?

20 year patent over in 1975?

[jirushi]

Merry Christmas.

@lightning22, yes the quality of the Taiyo's is good, but I have a feeling that the power curve will be very steep. There is a big column of CO2 exiting the barrel after the pellet has left, which can't be a good sign, economy-wise. I think I will need to increase the valve return spring strength. And do more testing.

A few differences with Crosman 160/QB78: on the Bobcat, the hammer is cocked by pulling the bolt backwards instead of pushing it forwards.
The Bobcat has a safety, but it isn't automatic like on my 2nd series 160 (I prefer non-automatic; it is annoying to press the trigger and realise you've forgotten to take the safety off!). And in the Bobcat the second CO2 capsule isn't pierced (I must check if a Crosman 160/180/400 tube cap fits).

@Mark, thanks. I think that repairing airguns, especially when the process is straight forward, is my favourite part of the hobby.
@ 45flint, you are probably right. Rudy Merz's designs must be the most copied CO2 airgun designs ever?
The Taiyo Juki Junior is a copy of the 180 by the way.

Crosman 160 2nd series (I think the white o-ring should be on the tube cap btw, and the black one on the valve body, oops):


Possibly the 380 is even closer to the Crosman 160 and QB78:


Junior (source: http://anotherairgunblog.blogspot.co...mbly-part.html)

[jirushi]

Some more info:

Taiyo Juki was a trade-name used by Miroku (Miroku Firearms Manufacturing Co.) of Kochi, Japan, making airguns in the 1970's. Taiyo Juki also made Winchester 37 clone shotguns.

They were imported by Kassnar, Harrisburg, Pennsylvania.

Miroku also made firearms for Charles Daly, Browning, Winchester and others.

Source:
https://www.gunauction.com/buy/16598...-BClDT5lsI2gWm

[Lawrie Amatruda]

Merry Christmas.

@lightning22, yes the quality of the Taiyo's is good, but I have a feeling that the power curve will be very steep. There is a big column of CO2 exiting the barrel after the pellet has left, which can't be a good sign, economy-wise. I think I will need to increase the valve return spring strength. And do more testing.

A few differences with Crosman 160/QB78: on the Bobcat, the hammer is cocked by pulling the bolt backwards instead of pushing it forwards.
The Bobcat has a safety, but it isn't automatic like on my 2nd series 160 (I prefer non-automatic; it is annoying to press the trigger and realise you've forgotten to take the safety off!). And in the Bobcat the second CO2 capsule isn't pierced (I must check if a Crosman 160/180/400 tube cap fits).

@Mark, thanks. I think that repairing airguns, especially when the process is straight forward, is my favourite part of the hobby.
@ 45flint, you are probably right. Rudy Merz's designs must be the most copied CO2 airgun designs ever?
The Taiyo Juki Junior is a copy of the 180 by the way.

Crosman 160 2nd series (I think the white o-ring should be on the tube cap btw, and the black one on the valve body, oops):


Possibly the 380 is even closer to the Crosman 160 and QB78:


Junior (source: http://anotherairgunblog.blogspot.co...mbly-part.html)

Louis,

The best way to reduce the waste of Co2 in your gun is to fit a weaker hammer spring, or shorten the existing one, or another way is to shorten the valve stem slightly.

Cheers, Lawrie.

[jirushi]

Louis,

The best way to reduce the waste of Co2 in your gun is to fit a weaker hammer spring, or shorten the existing one, or another way is to shorten the valve stem slightly.

Cheers, Lawrie.

Thank you Lawrie for the great tips!
I will soon have a little parcel filled with Streak valves and some Sharp ones too for resealing, if possible
First I must wait until the Christmas parcel madness is over lol.
Merry Christmas

[jirushi]

A little update:
I found a Miroku scope. Must be rebranded, but for the same company that produced the Taiyo Juki Bobcat.
I think this scope was made after the Bobcat. Perhaps eighties? It is too big for the gun.
The Ednar might be a better fit, but I think the slim German Haweka is perfect.
Collecting scopes is just another disease?

[jirushi]

I am tinkering with the Taiyo's.

They are the worst gas hogs I have.
I got 10 shots out of the .177 until velocity started to decrease rapidly. That's on 1 "powerlet".
De second powerlet isn't pierced, but serves as a spare (?).

Mods so far:

- shortened hammer spring (I used a spare Crosman 180 hammer spring)
- stronger valve return spring
- beer can rolled up to sleeve the inside of the valve.



- o-ring around the valve stem inside the valve, to reduce/prevent CO2 leakage via the stem.
I am using a Crosman 160 valve, which has a thinner stem. The o-ring seems to be working well as I don't feel any CO2 blowback from the action during the shot.



- narrower tp > haven't finished this project yet. I've modded a delrin QB78 tp, not sure if it will work in the Taiyo.
- two o-rings in the hammer tube to reduce hammer bounce:



- thumb tack glued on inside of tube cap; it worked, so the gun can use its two CO2 capsules now

[jirushi]

The mods above, minus the thumb tack, improved shot count from 10 to 30 (on 1 CO2 powerlet).
Using 8.44 gr JSB 4.53 mm.
With velocities ranging from 175 to 193 meter per second (192 to 212 ft/s).

Velocities before the mods were around 210 ft/s, so I think the gun is still at its max.
This probably means that I still have CO2 waste, but less than before.

One factor is the huge hammer. 62 grams.
Frakor is going to modify a two power Crosman 180 hammer, which weighs 51 grams.
Otherwise I could drill a hole in the Taiyo hammer, but I'd rather keep that original.

Tinkering with CO2 guns - more fun than any other type, imo.

[jirushi]

An update.

The two-power, lighter Crosman hammer idea doesn't work. Maybe there is a way to make it work, but for now the Taiyo trigger sear cannot grip the Crosman hammer well.
However, frakor did a great job at drilling the hammer pin hole at the right place in the hardened steel:



I should probably concentrate on the hammer spring and valve return spring to improve consistency, although I am already quite happy with the 30 shots at an average of 590 ft/s (8.44 gr JSB), per CO2 capsule.

Miroku scope: from the same manufacturer as the Taiyo. Too big for the gun and awkward pellet loading; too low. But really clear and surprisingly light.





Simple 4x20 Kassnar scope, pretty bright. Ugly on the high mounts, but the only way for comfortable .177 pellet loading. Plus I can still use the opens with these see through mounts.

[Geezer]

Brilliant stuff.

I’m assuming that Miroku scopes were just a regular Japanese scope branded for them, rather than them owning a scope factory too?

[jirushi]

Brilliant stuff.

I’m assuming that Miroku scopes were just a regular Japanese scope branded for them, rather than them owning a scope factory too?

Hi Geezer, yes it must be rebranded.
It's a good quality scope. Probably made for firearms. I must check the parallax.

I've finished finetuning this Bobcat.

This morning's shotstring, at 15.5 degrees Celcius. 8.44 gr 4.53 mm JSB's.
About 10 seconds between shots.

In meters per second:


That's about 23 useable shots between 604 and 571 ft/s. On 1 CO2 capsule. Not sure whether this is good or not, shot count wise for that kind of power.
Useable for plinking, up to 25 meters? Will test soon.

The "exploded view diagram" above wasn't 100% correct btw. One part is behind instead of in front of the hammer.

This is what's in the gun now, plus an o-ring inside the valve, around the valve stem.