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Discussion Starter · #1 ·
Hi all
I am new here, some time ago i bought an CB400N on good price. The bike spend last 9 years in garage and I dont know what happed with it before, but for the price i paid it was worth a try.
Firts issues were to clean carbs to make it run on both cylinders (after 2 cylinder were working it didnt want to go higher than 6k rpm), second to change all gaskets on top end due to oil leaks, change the oil with filters. Most of the parts went without problem. Last thing after full assembly and run there were strange knocking on TOP end, so i set up the valves and checked the tensioner. Dadada tensioner was busted, the screw that goes thru the cylinders was to short (previous owner) and the nut on it didnt screw on. Disassembly, fix the problem and bah, due to my mistake, i forgot about golden rule. Never trust antyhing that was done by previous owner. The cylinder head screws were mixed up and shorter one was at front, damaging the threat in block, yeah i know. So now need to fix it and change the screws to proper order and after that find out why it does not want to rev higher.

yeah this will be done, MOT will be done and saving money for further mods will began. the idea is to build street bobber
 

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Nice looking bike there Bart.

Sounds like you're pretty handy with the mechanical stuff, looking forward to sharing experiences with you.
 

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Discussion Starter · #4 ·
not my skills, but its good to have professional photographer friends :D i am just an engineer, soon to be MSc hehe photo art not my thing but i know some of b&w photos will be printed and end up at my wall ;D
 

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Discussion Starter · #5 ·
and i found next issue, previous owner not only mixed up the cylinder head bolts but also lost longer one and replaced it with shorter, as manual says 4 at front should be longer than 4 at the back, 1 long with rubber and 1 short one which goes to the inner left side. Due to the fact that only half of the thread was stripped i used thread tapper to repair the stripped one and redo the second good half. Now only to make the long bolt and hopefully everything will play. When everything will be assembled, I am gonna connect other batter and check if this is the problem of not reving higher than 6k, if not will dig more into the problem...
 

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Discussion Starter · #6 ·
Hi all, have small question coz in manual its called spring but what exactly does it responsible? It screw into the carbs, it has spring and jet shaped head, anyone? is it air mix screw and what position should it be set? its now 3 turns from fully in
 

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The brass screws in each carb are the idle mixture screws. Adjust the idle speed to 1200 rpm then adjust one mixture screw to achieve maximum idle rpm. Readjust idle speed to 1200 again, adjust the other mixture screw to achieve maximum idle rpm, then adjust idle to 1200 rpm. All done.

3 turns out is probably a little rich, 1 1/2 to 2 turns us more usual.

This adjustment shouldn't have any affect on high rpm operation.
 

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Discussion Starter · #10 ·
still waiting for the cylinder head bolt I decided i will try some photo shooting, as b&w pics were my friends i set up monochrome at my cannon and took some pics
 

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Discussion Starter · #15 ·
Hi guys
Damn it, i still have that weird knocking sound on the top of the engine, I am pretty sure that this is due to timing chain and its tensioner. last time i stripped the engine and change that lower bolt from tensioner, reassembled the engine and it still makes that stupid sound. In manual they say to loosen the lower nut ( tensioner is bolted by upper bolt to cylinder head and by nut to the cylinders) and idle, it will adjust. But i tried to do that and did nothing, its like it don't adjust it self ;/ maybe unbolt the upper one to be loose, lower nut and that idle it sacrificing some oil that will come out of those holes... what do you think guys any suggestions? and checked with other battery and still dont want to rev higher than 6k ;/ hmm... some major problems still to overcome before it will be fully functional.
 

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Discussion Starter · #16 ·
:twisted: I manually adjust the tensioner and no more knocking sound, good, one thing less. Even took it for a ride today, what a great feeling even thou i cant rev high no problem to drive 70 km/h on 5th gear. Just noticed that the mixture can be to rich and when suddenly shut the throttle it blows so i need to get the combustion test done and carbs adjustment. And the last good thing that there is no more oil burning, when all cylinder heads are at their place, with new gaskets, everything is sealed ;D good day must say
 

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verbel said:
:twisted: I manually adjust the tensioner and no more knocking sound, good, one thing less.
Excellent, glad to hear it, nice to be able to knock something off the list. How did you manually adjust the tensioner? I finally got around to looking at my 400T the other day and had a bit of chain noise that didn't change with the normal adjustment via the nut. At least I think its the cam chain, so I'm interested in how you did it so I can determine if this is my issue. Did you just take off the valve cover and push down on the top of the tensioner?
 

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Discussion Starter · #18 ·
HerrDeacon said:
Did you just take off the valve cover and push down on the top of the tensioner?
Yeep, just took the cover, loosen both lower nut and upper bolt, took screwdriver and push as much as i could, than tighten the bolt and nut, check the tension and vualla, pretty tight but in reasonable matter. I thought on that last night and found this to be the best solution and it worked out, you shouldn't trust the 32 year old mechanisms like tensioner to adjust by it self, a little push is advised ;P
 

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Discussion Starter · #20 ·
no problem mate,hope will work for you. If you have any tips on how to properly adjust that damn carbs feel free to post. Does the fact that thay may be not synchronized can be a reason that it does not want to rev high and choke at around 6k??
 
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