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CB200 jet advice

JohnCB500

Veteran Member
Joined
Jun 8, 2020
Total Posts
108
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Location
Hereford
Hi,my CB200 is running on foam air filters,using the original centre with foam wrapped around, not pods.the original were filthy dirty and replacements impossible,

It runs tickover and low down ok,

But will not rev past 7k on full throttle, it to lean,

How have you jetted your carb?

Hints on main jet size would be helpful

Thanks

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I'd be surprised if simply changing from paper to foam would make it run that lean. Back in the day I can remember running my CB175 without any filters on at all, and it would still rev to an indicated 10.5k and beyond. Also taking the silencers off and running it on open headers around the track back when Gaydon was still a club race circuit. And this didn't burn out the exhaust valves as some bystanders warned me, :geek:

Have you tried raising the needles in the carbs to richen the mid range mixture ?

( Reason I ask that is because I've recently been fiddling with my SL175. With the needles in the middle clip it would rev to redline but had a flat spot in midrange. Dropping the needles to lean off the mixture got rid of the flat spot but it is now not so keen to rev, topping out at around the 8.5k mark. This on Chinese carbs, but sure the theory is the same )

Cb200 has 88 mains in carbs with (IMHO) same venturi size as the CB175, which has 98 mains. CL and SL 175s, with their arguably more restrictive exhausts, run 92 mains.
 
Yes,raised the needle one slot,

As I said it runs ok until about 7k on full throttle, then starves

Close the throttle a little and it runs at 6.5k ok,



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So when it hits 7000 rpm it's not blubbering, like the choke was still on a bit? Have you tried using a little bit of choke to see if it improves?
 
So when it hits 7000 rpm it's not blubbering, like the choke was still on a bit? Have you tried using a little bit of choke to see if it improves?
Sorry for the delay,

Will do plug chops when running as fast as possible,

Then do choke test, although, increase the suction shouldn't increase flow through main jet if it's at maximum already,

Back later

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Then do choke test, although, increase the suction shouldn't increase flow through main jet if it's at maximum already,

No, but it will slightly restrict the amount of air mixed with it so it should make it a tad richer.
 
I burned out the paper and wrapped unifoam around the original air boxes on my cb200t, standard carb settings per manual. No issues when the carbs are actually clean.
Your previous thread https://www.vintagehondatwins.com/forums/showthread.php?2783-Out-and-about
suggests it was running well after the carb rebuild with cruizinimage kit but before modifying the original air filter paper to foam, correct? As long as the rubber tubes weren't damaged on the boxes I would assume the carbs require re clean. Might also want to make sure the o-rings on the little intake manifolds are sealing as fiddling with the carbs can effect that (especially if they were never changed since the 70's).
 
I know its been a longtime,but its winter,cold and damp,limited timeto ride on the bikes,
I think the issue is sorted,
it seems the contact breakers had to big a gap,sothe coil ran out of sparks so to speak above 7k revs.
reducing the gap to 12thou has helped tremendously ,

My defense is I am not used to CB ignition,all my other bikes are Electronic,,.


thanks for all your help,any advice on the ignition system willbe appreciated
 
I know its been a longtime,but its winter,cold and damp,limited timeto ride on the bikes,
I think the issue is sorted,
it seems the contact breakers had to big a gap,sothe coil ran out of sparks so to speak above 7k revs.
reducing the gap to 12thou has helped tremendously
,

My defense is I am not used to CB ignition,all my other bikes are Electronic,,.


thanks for all your help,any advice on the ignition system willbe appreciated

Glad you got it sorted.

Hmmm... so the points gap really DOES matter. :huh: Yeah, don't listen to Common Motor. :rolleyes: (not saying you did, just confirming the obvious)
 
Gentleman, and ladies

Just to say, the problem appears to have been solved,


I fitted a cheap replacement coil from China, it had a 3.5ohm primary circuit resistance,

Now it runs sweetly up to over 9k

Just as it should

Took it out today, like riding an armchair
e88ceeac06819136c73855557e1f05ff.jpg


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