MC90 Engine Rebuild - Carbs

[TJ Ledwith]

Hey there,
Currently trying to restore an MC90 for a go kart my dad and I got about 5 years ago. I had posted on here around that time but had no clue what I was doing (still not much different than now) and didn't even have facial hair yet. It's been on the back burner for a while but now that I'm older and have dipped my toes in various mechanical projects lately I think it's time to get this kart running.

I've torn apart the engine and am in the process of cleaning it all up. The block is in pretty good shape. Bottom piston ring is stuck so I cleaned it out and ordered what I am hoping is the right replacement. I have been trying to do some research past couple weeks on things like carb rebuild kits, piston rings, pistons, etc. I found the book "Small air-cooled engines service manual" from a while back that includes info on the MC-90 and other McCulloch engines. My dad had bought the MC90 IPL years ago on ebay but I can't find it and can't find the IPL online. It seems to me (correct me if I'm wrong) that the MC-90 shares a lot of parts with the MC-100 and MC-49, so I've been using the MC100 IPL to reference for some parts. It has the same carb that I have (48890B) and seemingly same piston assembly. Still pretty beginner to all of this so any knowledge that might be helpful is appreciated.

I have a twin carb setup (both 48890B flatbacks) but cross referencing the different names for carbs and trying to find similar carb rebuild kits has been tough. I found two kits that I've been considering -- one from Sugar Creek Supply (MAC-9 kit) and another from Discount Marine Parts. Not sure on the reputability of DMP, but the kits offered seem more complete (needle, expansion plugs, etc.).

Long story short, anybody have recommendations for carb kits for the 48890B flatback carb or can point me in the right direction for finding similar enough kits that would work. Would most of the flatback carb kits I've been seeing work, many look very similar to my gaskets just some minor differences with a slot mine has that I don't think does anything. How crazy would it be to just get the material and make it myself?

[Rob Voska]

I don't mess with flatback carbs. Anyone know anything about the rebuild kits to help this young man?

[REAR]

Go to the top of the page and there are links to the McCulloch IPL's.

http://rearenginekarts.com/phpbb3/viewt ... f=1&t=4694

R.E.A.R.

[TJ Ledwith]

Go to the top of the page and there are links to the McCulloch IPL's.

http://rearenginekarts.com/phpbb3/viewt ... f=1&t=4694

R.E.A.R.

Yeah I've checked on both the REAR site IPL list on that link and the smallenginediscount website that was listed too, neither have the MC90 IPL. I've looked pretty extensively online, but maybe I overlooked it somewhere. I could swear I have a physical copy in my house somewhere...

[Terry Sullivan]

Here is the IPL, but I can't help with flatbacks

Mc-90IPL.doc

(843.5 KiB) Downloaded 206 times

[TJ Ledwith]

Here is the IPL, but I can't help with flatbacks

Mc-90IPL.doc

Thanks for the IPL, this is a huge help. I really appreciate it, saves a lot of guessing. I bought the wrong piston rings--no wonder they didn't fit properly yesterday when I got them.

[Larry Brown]

Check with Terry Ives, he can help. He will have the diaphrams for the flat backs





Larry Brown