I have still a problem with lower cylinder not getting hot, motor ticks over fine and will power up to 6000rpm after that it's flat and at max throttle wide open will only revs to 9000 rpm. lower cylinder dies and no smoke at exhaust and what gas there is at the exhaust is cold comparing with the other exhaust. have interchanged plugs,coils, pgm-11's and striped and checked over carbs,I have not yet check compression's as it feels quite good at the kick start with both the same , I am thinking it may be crank centre seal is leaking, just wondered if anyone has come across the same issue in the past?. any help would be appreciated.

id say its a blocked main jet in the lower cylinder.

you will need to compression test both cylinders.

check each cylinder for spark.

if you have both then its a fuelling issue.

rip the carbs and clean again and make sure the carb breather pipes are not blocked

cheers
i will check compression's first.
any idea what psi is good?.

For the compression test remember that the engine must be warmed.
For a good engine your readings must be about 130psi with as small as possible difference between the two cylinders.
Anything under 115psi is not good.
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Owner of : Honda NSR250 MC28 95sp colours / Honda NSR250 MC18 R6K SP / Honda RS250 NF5 89 in boxes / Honda C50 12V cub / Honda C50 12V super cub Japanese version /Yamaha XT600 89 benetton

Just reverse the spark coil first and see what'll happen,my guess is that rear cylinder wont work

He did it. He wrote it at the first post.
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Owner of : Honda NSR250 MC28 95sp colours / Honda NSR250 MC18 R6K SP / Honda RS250 NF5 89 in boxes / Honda C50 12V cub / Honda C50 12V super cub Japanese version /Yamaha XT600 89 benetton

I remember one time,like 16 years ago,both my coils have died on my '88,the rear one was working but not properly and the other was totally off,i was about to strip the engine,when a friend of mine came with a nearly new mc21,we've talked about the problem and told me to use his coils..Problem solved

Thats why i use HRC RS250 coils on my NSR's.Last time with stock coils was 5 years ago at Megara track with my MC18R6K when the coil of the front cylinder died and i lost the last section.But i think the discuss about coils is out of topic.
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Owner of : Honda NSR250 MC28 95sp colours / Honda NSR250 MC18 R6K SP / Honda RS250 NF5 89 in boxes / Honda C50 12V cub / Honda C50 12V super cub Japanese version /Yamaha XT600 89 benetton

compression's checked out not too bad with 120 top and 115 lower.
i will investigate further before striping the engine apart and thanks for your input

Compression sounds normal.
Yes investigate it before striping the engine .
Do some other checks.
Check the reeds if any is broken or if they have stuck.
Also a vacuum test will help to find if a crank seal is leaking.
I wish you good luck.
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Owner of : Honda NSR250 MC28 95sp colours / Honda NSR250 MC18 R6K SP / Honda RS250 NF5 89 in boxes / Honda C50 12V cub / Honda C50 12V super cub Japanese version /Yamaha XT600 89 benetton