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Author Topic: Doctor Funk, or, the strangest CT90 you've ever seen  (Read 927 times)

Offline SONIC.

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Re: Doctor Funk, or, the strangest CT90 you've ever seen
« Reply #30 on: Jun 30, 2017, 13:04:33 »
Guys can I has my thread back?




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Um..

No?

« Last Edit: Jun 30, 2017, 13:06:34 by SONIC. »


Offline XS750AU

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Re: Doctor Funk, or, the strangest CT90 you've ever seen
« Reply #32 on: Jul 17, 2017, 00:16:35 »
The entire picture is a "what not to do". We were trolling a fb welding page when we took that picture.

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Lets hope he does not start playing with it while sitting on that!

Offline cbrianroll

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Re: Doctor Funk, or, the strangest CT90 you've ever seen
« Reply #33 on: Jul 17, 2017, 00:32:38 »
Love the saw grinder..... we modified a skilsaw  once to run an 8 in blade instead of 7,  bad idea.....really close to getting stiches, other than that it worked great.

Offline Ryan Stecken

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Re: Doctor Funk, or, the strangest CT90 you've ever seen
« Reply #34 on: Jul 17, 2017, 03:07:00 »
Rad dude

Offline nateb

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Re: Doctor Funk, or, the strangest CT90 you've ever seen
« Reply #35 on: Jul 17, 2017, 03:31:56 »
Bitchin


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Offline advCo

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Doctor Funk, or, the strangest CT90 you've ever seen
« Reply #36 on: Jul 24, 2017, 15:02:15 »
I pulled the head yesterday out of curiosity. It does indeed have a big bore kit on it. Bore measures approx 54mm up from the stock bore of 50mm. According to a rough calculation this should put the actual displacement close to 104cc. Cool. Cam is stock. I put it back together (twice) since I broke off an intake stud and had to drill and tap it.

I picked up a stock 4-screw carb at Mid-O for cheap, cleaned it up and threw it together with some new gaskets. The throttle cable is too short so I'll need to make a new one before I can run it.

The carb that was on there was the #1 carb from a cb200 (i believe) which had a #38 pilot and #95 main. The stock carb for the CT90 that I put on has a #38 pilot and a #75 main. I am going to order a few jets since the plug actually looked pretty black I may be able to get away with running it a bit leaner.

« Last Edit: Jul 24, 2017, 15:04:10 by advCo »
"He broke the mirrors off his Cadillac, 'cause he doesn't like it looking like he looks back."

74 CB360 - Luna - http://www.dotheton.com/forum/index.php?topic=63294.0
82 GS550L - Tracker-ish - http://www.dotheton.com/forum/index.php?topic=67229.0 - Sold
74 XL350 - The Turd - http://www.dotheton.com/forum/index.php?topic=70252.0
Suzuki FA50 "No-Ped" - http://www.dotheton.com/forum/index.php?topic=71189.0
73 Suzuki RV125 -http://www.dotheton.com/forum/index.php?topic=73875.0

Offline vwrabbit

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Re: Doctor Funk, or, the strangest CT90 you've ever seen
« Reply #37 on: Jul 24, 2017, 17:54:17 »
I love these little 90s.  My uncle had one me and my brother tried resurrecting back in the 90s when we were teens.  I believe we got it running, but that's about it.

Offline pacomotorstuff

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Re: Doctor Funk, or, the strangest CT90 you've ever seen
« Reply #38 on: Jul 26, 2017, 11:46:49 »
I think I can shed a little light on the extended oil filler / dipstick.
It is probably an aftermarket breather (though might have been a CYB part) to help relieve internal pressure.  At high rpm's, the single little breather of the stock engine can't handle the pumping pressure and starts to puke oil and can even blow a seal, so the additional breather helps get rid of the pressure.
The stacked plates in the extension act like a series of baffles to knock down any flying oil droplets, so it gets returned to the crankcase.
The first one I ever saw was in the mid-sixties on the CB450 that Jim Odom raced at Daytona, though I believe various racing Honda factory racers and conversions used them.
It's such a cool piece, I may try to coerce my machinist into building one for my 175 twin over the winter.
I know it seems odd in the day of 600cc "beginner bikes", but the Honda 90 slopers were road raced back in the day and a huge amount of performance equipment could be had - you've got the big bore kit and if you had the stroker crank from Powroll, it would go out to 133cc.
And yes, it is the strangest CT90 I've ever seen.
A great ride.
Pat

Offline advCo

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Re: Doctor Funk, or, the strangest CT90 you've ever seen
« Reply #39 on: Jul 26, 2017, 12:52:51 »
Thanks Pat! Very cool info on the breather. Some of the mods that have been done are nicely done, others not so much but once I clean up the mess I think this will be a fun little scooter.
"He broke the mirrors off his Cadillac, 'cause he doesn't like it looking like he looks back."

74 CB360 - Luna - http://www.dotheton.com/forum/index.php?topic=63294.0
82 GS550L - Tracker-ish - http://www.dotheton.com/forum/index.php?topic=67229.0 - Sold
74 XL350 - The Turd - http://www.dotheton.com/forum/index.php?topic=70252.0
Suzuki FA50 "No-Ped" - http://www.dotheton.com/forum/index.php?topic=71189.0
73 Suzuki RV125 -http://www.dotheton.com/forum/index.php?topic=73875.0

Offline advCo

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Re: Doctor Funk, or, the strangest CT90 you've ever seen
« Reply #40 on: Jul 26, 2017, 13:09:02 »
I trimmed and connected the throttle cable last night. The outer jacket on the existing cable is in 2 pieces held together by some electrical tape (lol, sounds about right) so I need to run a different cable eventually - the throttle doesn't snap shut due to binding somewhere along the way. Its short enough that I should be able to put a new jacket on the inner cable and hopefully fixes my issue.

Gave it a few kicks last night but I think my timing is off from when I pulled the top end.

Did some research and it looks like with the stock carb and 54mm kit I will need to be at about an #80 on the main jet. Can't find these jets anywhere so I'm going to have it drilled.
"He broke the mirrors off his Cadillac, 'cause he doesn't like it looking like he looks back."

74 CB360 - Luna - http://www.dotheton.com/forum/index.php?topic=63294.0
82 GS550L - Tracker-ish - http://www.dotheton.com/forum/index.php?topic=67229.0 - Sold
74 XL350 - The Turd - http://www.dotheton.com/forum/index.php?topic=70252.0
Suzuki FA50 "No-Ped" - http://www.dotheton.com/forum/index.php?topic=71189.0
73 Suzuki RV125 -http://www.dotheton.com/forum/index.php?topic=73875.0

Offline advCo

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Re: Doctor Funk, or, the strangest CT90 you've ever seen
« Reply #41 on: Jul 26, 2017, 16:47:57 »
Got this thing running again on the stock carb. It runs pretty good, had to back the idle screw out ~2 turns to get it to idle right without dying.

I'm still hearing a terrible knock when I get it into 3rd gear in the High range on the transmission, and there's basically nothing over 3/4 throttle. Even if I choke it at WOT it doesn't balance out, so I don't think its running too lean. Seems to pull ok through the gears in Low range, but if I crack the throttle going uphill or anything other than flat I get that ugly knocking sound. Any ideas?


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« Last Edit: Jul 26, 2017, 17:32:34 by advCo »
"He broke the mirrors off his Cadillac, 'cause he doesn't like it looking like he looks back."

74 CB360 - Luna - http://www.dotheton.com/forum/index.php?topic=63294.0
82 GS550L - Tracker-ish - http://www.dotheton.com/forum/index.php?topic=67229.0 - Sold
74 XL350 - The Turd - http://www.dotheton.com/forum/index.php?topic=70252.0
Suzuki FA50 "No-Ped" - http://www.dotheton.com/forum/index.php?topic=71189.0
73 Suzuki RV125 -http://www.dotheton.com/forum/index.php?topic=73875.0