Running on 3

[scooke]

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? 

[billy sugger]

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

[scooke]

I had a quick check, the last number is different which I presume means it would fit. 

[billy sugger]

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

[Bianco2564]

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 ?

[SloRider125]

I use FowlersParts (Rather than CMSNL, and It's easier to navigate)to find Blowup Diagrams of parts including part numbers. 

[Fozzie]

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.

[fastbob]

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 . 

[linuxrob]

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.

 

[Bianco2564]

OP, did you get anywhere with this?

[Bianco2564]

Where's that tumbleweed gif?

[Mississippi Bullfrog]

25 minutes ago, Bianco2564 said:

Where's that tumbleweed gif?

[fastbob]

 

Edited October 31, 2021 by fastbob

[Fozzie]

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. 

[bonio]

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.