1982 CB750K... Issues.. Issues..

[wraithen]

I just bought this bike (1982 CB750K with full windjammer and 30k original miles) from some guy who said he had it in his garage sitting for about a month.I am more inclined to believe its much longer than that by how the bike runs and the condition of the tires (I'm in new mexico and its super dry here and the tires are pretty dry rotted). Anyway, here are my issues. I'm mechanically inclined (I do all my own work on my cars) but this is my first bike so anyhelp or advice would be greatly appreciated.

1. All the rubber on the bike is dry rotted and most of its leaking a little. (I'm working on getting it all replaced)

2. The bike doesn't idle, you have to keep a bit of throttle in it to keep it going.

3. It backfires and pops.

4. The left most cylinder doesn't seem to be fireing. The pipe on it doesn't even get remotely close to the same temperature as the other 3.

5. The throttle sticks when I shift, even if i manually force the grip back it sometimes keeps revving up at 6 or 7k.

So I'd like to do the work myself rather than have a dealer/shop charge me way to much to get it done. Where do I start besides the dryrot?

[Rod_Knockin]

replace the carb boots and completely rebuild the carbs replacing all of the seals and needles. Drain the tank and make sure there is no rust inside otherwise you will be cleaning and rebuilding again soon. If there is any rust use a tank cleaner liner kit.

[wraithen]

that will fix the sticking throttle also?

[Rod_Knockin]

the carbs are constant velocity type. The throttle cable doesnt pull the carb barrel up. Instead the throttle handle operates a butterfly at the inlet of the carbs and vacuum pulls up the barrels. My guess your barrels are sticking.  If you had to force the throttle handle back I would recommend lubing or replacing the throttle cables too.

[wraithen]

thanks bro i really appreciate it.

[wraithen]

carb rebuild kits look pretty cheap too, so thats a good thing. do you prefer any website for picking them up? or just ebay as usual?

[Rod_Knockin]

there are many listed by users here. I like z1enterprises but I dont have any experience with anyone else but oldbikebarn.com and they were slow shippers.

[Rod_Knockin]

When You rebuild the carbs I recommend changing all of the soft ass phillips head screws with stainless socket head or torqx (spelling?). The soft phillips are a bitch to get out if they are stuck. They strip very easily too. You will thank yourself sometime in the future.  

[wraithen]

Just to update (it's a miracle i actually rode this bike home, apparently these bikes are bulletproof), I removed the carb and its rusty as hell inside of it, just covered.. the valves and everything. It's way overdue for a cleaning/rebuild, the intake boot clamps where barely on, in addition to being cracked and the air filter was soaked in fuel and really really dirty. Good news is the tank looks gtg internally. So heres the plan atm.

1. Carb is being rebuilt as we speak.
2. Replacing the intake boots.
3. Replacing the air filter.
4. Replacing the tires/tubes with Dunlop D404 and applicable innertubes.
5. Replacing spark plugs.
6. Throwing some chain wax on the chain.


Then wish me luck, I'm gonna go for a ride.. The parts should all be here this weekend or early next week. Bikebandit.com is a pretty helpful/cheap/easy to use site.

[Rod_Knockin]

I still recommend that you replace the soft Phillips head screws on the carb with stainless socket heads. The phillips head screws are soft and if they get stuck they strip very easily. I had to cut slots in the head  to use a standard screwdriver in 3 of the screws to get them out. I just rebuilt my carbs again. My bike runs great. Better than it has in years.

[wraithen]

ya thats cool man. im totally doin that. i was super suprised how screwed up the carb was and the bike still semi ran. i can't wait to see how it runs when its all good to go

[Rod_Knockin]

Make sure the carb slides move freely. I tried to use silicone to lube them but it didn't like that. The slides should move up and down freely and quickly. Its a great bike to ride when its running good. Lots of power. Its an easy bike to love. I had mine since 1987 and cant find a reason to replace it.

[wraithen]

i just finished the carb its good to go now. the number 4 carb (the one that was inop earlier) was missing some internals... i dunno wtf is going on with that but its good now. ill install it tonight and we will see if she behaves a bit better. i'm still waitin on the rest of the parts in the mail.. they should be here on monday.

[woodsrider250-2]

Missing internals will do it every time...LOL!

[wraithen]

Updating on my 1982 CB750K.


I just put in the rebuilt carb and all new intake boots, drain lines, changed the oil (it was naaaasty) and filter, replace the air filter, and replaced the spark plugs (they where bad too.. really bad). I put gas in it and it is running so nice now. I set the idle to 1k and rode it around a little bit today and it's running strong.. it started right up and had no issues engine wise i could see. I still need to get the tires changed, i have them, i just didn't get a chance to do it today. I did notice a few new issues though unfortunatly..

1. the forks have about 0 pressure.. they bottom out and clang at every bump.. not good. so do i just replace the seals/bearings ect and reservice them? or what do i do with those?
2. i have a very small gas leak coming from somewhere in the carb area.. not sure yet, i need to dig into that a bit more, but it's very very small (about a drip every minute or 2).
3. the chain is pretty old.. i think it's time to change it, it's not locked up yet but it definitly needs some assistance.
4. i wanna take off the windjammer and install just a regular headlight assembly.. anyone know of a kit for that?
5. do they make seats that will work with this bike that have a backrest for me? not just a sissy bar for the passenger. i'm lookin around on the internet like crazy and can't find one.

Thanks guys. STJ

[TS750c]

where did you get your velocity stacks from?

[wraithen]

what r velocity stacks?

[TS750c]

i thought that was the name for the little rubber boots that hold the carbs on the intake? maybe it isnt.... but anywho if you did get those boots i was wondering where you got them from?

[wraithen]

just google intake manifold boots for ur year of bike. i was suprised that a buncha sites carry them including ebay. I got mine from bikebandit.com.

[TS750c]

ok awesome thanks man, atleast i think that is the problem and if i get them i hope that will cure the problems. good luck!