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Discussion Starter · #1 ·
Hi guys. Just found a nice '81 6K 400A that had been in dry storage for 30 years, so I have a bit of work to do. Need a manual - any still available? The tank looks pretty clean, but the carbs are frozen, along with the frt caliper. I pulled the carbs and got it to run on starting fluid. Sounded good. Oil is very clean but I was thinking to do a change with full synthetic 10-40. Thought I'd start with soaking the carbs and caliper in Liquid Wrench or something and maybe denatured alcohol for the tank. What are people's fav fluids here? New to this and open to ideas. And what about individual air filters -K&N? A bit of rejetting needed I know.
And a general question on carbs. Coming from an old sports car background (MG's, Alfa, BMW 2002), while seeing the good in motorcycle carbs, I was wondering on twins, for example why nobody seems to use a properly setup single dual sidedraft carb like a weber 40 DCOE or Mikuni, avoiding the need to sync carbs. I did see a custom 4 into 2 setup on a 750 using a Mikuni of some sort. Just wondering about alternatives if my carbs prove to be unuseable. Excited to get my new blue baby on the road and would appreciate any input. Cheers, Ron
 

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Several members have gone the single carb route but I havent seen a lot of results. The carbs are very easy to sync so your choice. The 400 a has a torque converter that doesnt like synthetic oil , use 10/40 motorcycle oil with wet clutch protection. I know ,no clutch plates its the additives in the oil that you want.in the motor. I like Deep Creep and NAPA carb cleaner. Others have different choices but most are good.

Bill H
 

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Discussion Starter · #3 ·
Thanks for the tip on the oil Bill. For starters, I bought a gallon of PB Blaster and am soaking the carbs and caliper in that to free things up before I start cleaning/rebuilding. What sort of single carb? I was wondering also if some have used a single larger carb from 4 or 500 cc single of some sort. Cheers, Ron
 

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I would urge you to stick with the original carb set up, because experimenting with unusual carbs necessitates a lot of modification and is unlikely to result in the engine running as well as it should. Carbs can be cleaned ultrasonically, and can usually be made to work, but very high mileage carbs can have wear that will affect their performance. ie. the slides need to be a close fit in their bores otherwise air leaks round the slide and it's difficult to obtain smooth pick-up from idle.
 

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There should be a filter on the petcock up in the tank . You cant see it unless you take the petcock off. I dont think you will gain a lot if anything by going to one carb. Honda built the air intakes ,carbs and exhaust system to get the max performance from the motor and any changes will require changes in the jetting and unless you are building a racing engine will result in less performance.
If you pay shipping to and from and send me the carb bodies and jets I will clean them ultrasonically for you .Just a thought. If you go to the single overhead cam section of the forum and look under the fuel section the may be an old post on the single carb change. I have read posts on the subject but I dont think any one has made it work. there is also one on adding a turbocharger.. the cam and carbs are different than the non auto bikes so dont know if the info would help.

Bill H
 

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Discussion Starter · #7 ·
Thanks for the info and offer Bill. I'll think on it. Location? I'm in Ohio. I'll see what they look like after soaking in PB Blaster for a day - mainly to free them up, as they were frozen. Not really looking to make big changes - just thinking about alternatives if they turn out to be unuseable. Cheers, Ron
 

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Discussion Starter · #9 ·
Columbus here. Throttles are still stuck even after 24 hr soak in PB. Ever seen that? Slides were varnished pretty good but cleaned those off with acetone. Ultrasonic would probably be a good idea for the rest. Probably should throw in rebuild kits too but gotta get the throttle plates free before I do anything else. I wouldn't think varnish is the culprit. Would a careful bit of torch hurt?
 

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Do you have the carbs apart? Hair dryer or heat gun dont think I would put any flame on them. I have seen some parts take days to free up so keep soaking a while yet. Where did you buy the rebuild kits. Some kits dont have the right brass bits and all you can use are the gaskets. Polish the slides with 1000 grit wet or dry paper. You may have to replace the throttle shaft felt seals .If you cant find them you will have to make them. When you get the shafts free remove the plates and pull the shafts for better cleaning. Mark the plates so you can get them back in the proper place. They will fit in other positions but wont work properly .

Bill H
 

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Discussion Starter · #11 ·
I don't have the kits yet. You seem to know more about these carbs than I ever will. Interested in taking on the rebuild if necessary after cleaning isn't enough? I have other projects I could work on in the meantime. $?
 

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I am 80 years old ,have closed my shop and am not taking on any more work. I just thought I would help you out by cleaning them. Problem with the old carbs any thing can happen, you could strip a screw or bolt or a jet. , break a jet off or something else and damage the carb were its not useable. I dont want to call you up and say hey I screwed up and you will have to find another carb.

Bill H
 

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Discussion Starter · #13 ·
Gotcha Bill, tho I'm not that far behind you being a 49'er :) Cleaning would certainly help, tho I'd love to get the throttles unstuck first. Maybe more soaking, then take a run down there to drop em off? Did that ride many times as part of TOSRV in my bike racing days. IIRC my top time was about 5hours. Should be a little quicker on a motorcycle :) Sometimes we'd have a buddy pace us/break wind on a training ride with his BMW R60 and sidecar. Those were the days!
 

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I remember the TOSRV . I am a retired park officer and worked the tour at Lake White State Park from 86 thru the mid 90s.. If you made the stop at Lake White I live one mile from the park office.
It only takes about 30 minuets to run thru the cleaner .If you want ride down let me know ahead of time and I will have it ready and do it while your here.

Bill H
 

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Discussion Starter · #15 ·
That sounds like a plan Bill, thanks. Maybe in the next couple of days and set it up with a phone call? Or email, tho I'm not sure what the rules allow here, or how to PM being a newbie. Let me know. I'm resoaking the carbs in PB currently hoping to free up the throttles. Cheers, Ron
 

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Hi Ron. I will have company this week and be out of town for the 4TH I will contact you on the 5TH and set up a time to get together. There are several places that sell kits. You might try your Honda dealer. I like Sirius Consolidated problem with them is they sell thousands of kits and nothing is listed in order .You may have to search thru a lot of pages to find what you want.


Bill H
 

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It doesnt much mater who the vender is. Only buy kits from Japan. If you can wait a few weeks CMS has the correct parts . They are across the pond so shipping cost and wait time is a little more but you get the correct parts. Do you have the carbs torn down. You have both the air cut valves and the fuel pump valves how does the rubber dia look on the valves . They dont come in the kit and have to be bought .

Bill H
 

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Thanks for the tip on the oil Bill. For starters, I bought a gallon of PB Blaster and am soaking the carbs and caliper in that to free things up before I start cleaning/rebuilding. What sort of single carb? I was wondering also if some have used a single larger carb from 4 or 500 cc single of some sort. Cheers, Ron
Stock carbs are fine give it good cleaning clean float bown make sure 2 nuts holding carb on are tight set 1 adjustment for 1 turn set floats to shut off fuel when bowl is full clean needle valve good and should be good to go replace battery with new from batteries and bulbs be great see if you have good blue spark and run it
 
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