scooke Posted October 19, 2021 Share Posted October 19, 2021 I've got a 1999-2000 honda cbr 600f4 (last of the carb model) passed mot but went to start it last night sounds like it's running on 3. I've got a built in volt metre and that's reading 75% full when riding and only 63% when stopped. % didn't increase after ride. The carb diaphragm was a little worn when I put it back together so would I be correct in thinking both need replacing? If that is the case would a 1997 diaphragm fit onto the carbs? Quote Link to comment Share on other sites More sharing options...
billy sugger Posted October 19, 2021 Share Posted October 19, 2021 Have a look on CSMNL, (consolidated motor spares Netherlands limited) search under Honda for your bike, then check the exploded diagrams for carbs, find the part no for the diaphragm, then do the same for the other model. If numbers are the same your good to go Quote Link to comment Share on other sites More sharing options...
scooke Posted October 19, 2021 Author Share Posted October 19, 2021 I had a quick check, the last number is different which I presume means it would fit. Quote Link to comment Share on other sites More sharing options...
billy sugger Posted October 19, 2021 Share Posted October 19, 2021 1 minute ago, scooke said: I had a quick check, the last number is different which I presume means it would fit. Probably not, the numbers should be jdentical if it's the same part. Have another look and see if you can compare the two together Quote Link to comment Share on other sites More sharing options...
Bianco2564 Posted October 19, 2021 Share Posted October 19, 2021 When did you take the carbs apart, before or after it started running rough? From what I can tell the diaphragm and slide are all one piece, is that correct? What makes you think its a little worn, the diaphragm rubber needs to be perfect with no splits or perishing or it will not work. If the slide has some signs of rubbing where it moves in the carb, I'd say that's normal, obviously there are limits. When you say both need replacing, both what, there is only one diaphragm per carb? Looked at cmsnl and there are different letters aswell as the last number from a 97 to 99 model, so unlikely they are compatible. The volt meter should read around 14.5 when running and 12.5 when switched off, Did you check for a good spark ? 1 Quote Link to comment Share on other sites More sharing options...
SloRider125 Posted October 21, 2021 Share Posted October 21, 2021 I use FowlersParts (Rather than CMSNL, and It's easier to navigate)to find Blowup Diagrams of parts including part numbers. Quote Link to comment Share on other sites More sharing options...
Fozzie Posted October 21, 2021 Share Posted October 21, 2021 These bikes run quite rich from memory, the spark plugs needed changing at the intervals. What condition are they looking in? Also is the exhaust hot for all 4 pipes? That's a quick way to check if there's only 3 cylinders running, let the bike warm up and spray a bit of water on each down pipe, it should evaporate pretty much instantly. That's the first place I'd start anyway, often the simple things. 2 Quote Link to comment Share on other sites More sharing options...
fastbob Posted October 22, 2021 Share Posted October 22, 2021 I find it curious that your first thought is the charging system . Is it actually running on three cylinders ? Have you done a spit test on the downpipes ? If it is running on three then the cold cylinder is your culprit . Check the lead , plug cap and plug and then check the carb . 1 Quote Link to comment Share on other sites More sharing options...
linuxrob Posted October 22, 2021 Share Posted October 22, 2021 good advice as always Bob, check to basics first, my money would be on a vacuum carb balance pipe come adrift if it indeed on 3. 2 Quote Link to comment Share on other sites More sharing options...
Bianco2564 Posted October 31, 2021 Share Posted October 31, 2021 OP, did you get anywhere with this? Quote Link to comment Share on other sites More sharing options...
Bianco2564 Posted October 31, 2021 Share Posted October 31, 2021 Where's that tumbleweed gif? Quote Link to comment Share on other sites More sharing options...
Mississippi Bullfrog Posted October 31, 2021 Share Posted October 31, 2021 25 minutes ago, Bianco2564 said: Where's that tumbleweed gif? 2 Quote Link to comment Share on other sites More sharing options...
fastbob Posted October 31, 2021 Share Posted October 31, 2021 (edited) Edited October 31, 2021 by fastbob 1 Quote Link to comment Share on other sites More sharing options...
Fozzie Posted November 1, 2021 Share Posted November 1, 2021 Happens a lot on these threads now It used to be "Hi guys! Which 125 should I buy?" followed by radio silence. Some would turn up 6 months later having bought the Chinese bike we all told them not to buy. Seeing as the 125 market is pretty dead, I guess this has just replaced it. Quote Link to comment Share on other sites More sharing options...
bonio Posted November 1, 2021 Share Posted November 1, 2021 On 31/10/2021 at 07:47, Bianco2564 said: OP, did you get anywhere with this? Funny. The guy passed by here just the day before you posted. Quote Link to comment Share on other sites More sharing options...
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