[Phil keen]

hi
Hi guys , these plugs are 24 hours old and done 10 miles , the right one is very sooty
Both new ngk dr8es , right cylinder heats up quicker than left , new Honda recommended coils been fitted, new ht lead , cdi is working BUT bike misfires / jerks over 5.5k revs and I thought it electrical but do u think it could b carb related?
just to add , carbs have been manually and sonically cleaned and needles/jets ect replaced
Cheers all

 

[CXPHREAK]

Your problem may stem from the carb parts you replaced.

The original brass parts and float needle are likely best put back after cleaning.

Did you also fit aftermarket air cut valves?

 

[Phil keen]

Your problem may stem from the carb parts you replaced.

The original brass parts and float needle are likely best put back after cleaning.

Did you also fit aftermarket air cut valves?

Hi , I didn’t rebuild the carbs but from memory yes I was told it had the new air cut valves ,
Would carb not set up right make bike jump irratically over 5.5k revs ? I’ve been looking at electrical problem till I looked at the plugs after only 10 miles

 

[The lost Dane]

Hi
Your right cylinder is running lean
lean condition creates a hot combustion temp

 

[Sidecar Bob]

You have now started 3 threads about the same problem. Multiple threads about the same problem (even if attacked from different angles) are frowned upon because it gets confusing when people answer in one thread without reading the others or without realizing that they are all related.
I considered merging them but I think in this case that would only make it even more confusing so I am posting links to the other threads in each of them instead.

I strongly recommend reading all 3 threads before replying in any of them.

Cx500 b 1981 misfires around 5000 revs

Hi all just got a beautiful cx and it misfires around 5-6k I have bought a 2nd hand cod unit that was confirmed working because it had an ignitech on it and I didn’t know if it was mapped to the bike so put an old fashioned cod back on but still jerking at same revs but better and smoother...

www.cx500forum.com

Resistors in lead and caps

Hi all , dodgy cx running real bad after 5k revs , reading a lot on here about resistors in leads and caps , forgive my ignorance but I’m new to classic bikes (apart from my rd350lc) The guy who sold me the bike when I quizzed him said he replaced the coils, ht leads and plugs to Honda’s spec...

www.cx500forum.com

 

[wjvh]

To the original OP
1. How do you know R cyl is too hot?
2. The clean plug shows no evidence of being too lean, 10 miles of use is too few to determine that.
3. The sooty plug definitely looks like it is a bit rich.
4. I suspect the issues at 5k revs are caused by one or both cylinders being too lean.
5. Tune the air-fuel ratio on each cylinder. There is plenty of info available about that depending on
Which model you have. A colortune could be handy, personally I didn’t get on too well with that so have just fiddled with settings based on feel and plugs. Then balance the carbs.
6. as sidecar Bob says, easier for all, especially you, if issues with bike kept in one thread. 👍🇬🇧
7. good luck - you have a running bike so solution probably not too far off.

 

[reclinedrelic]

If you want to read your plugs to find the reason for your 5000 rpm stumble you need to do a plug chop. New plugs, ride at 5000 rpm then kill the engine, pull clutch and stop at side of road. Pull plugs and read them. That will give you some idea of what is happening at that particular rpm under load.

 

[Phil keen]

Hi
Your right cylinder is running lean
lean condition creates a hot combustion temp

To the original OP
1. How do you know R cyl is too hot?
2. The clean plug shows no evidence of being too lean, 10 miles of use is too few to determine that.
3. The sooty plug definitely looks like it is a bit rich.
4. I suspect the issues at 5k revs are caused by one or both cylinders being too lean.
5. Tune the air-fuel ratio on each cylinder. There is plenty of info available about that depending on
Which model you have. A colortune could be handy, personally I didn’t get on too well with that so have just fiddled with settings based on feel and plugs. Then balance the carbs.
6. as sidecar Bob says, easier for all, especially you, if issues with bike kept in one thread. 👍🇬🇧
7. good luck - you have a running bike so solution probably not too far off.

thank you

If you want to read your plugs to find the reason for your 5000 rpm stumble you need to do a plug chop. New plugs, ride at 5000 rpm then kill the engine, pull clutch and stop at side of road. Pull plugs and read them. That will give you some idea of what is happening at that particular rpm under load.

If you want to read your plugs to find the reason for your 5000 rpm stumble you need to do a plug chop. New plugs, ride at 5000 rpm then kill the engine, pull clutch and stop at side of road. Pull plugs and read them. That will give you some idea of what is happening at that particular rpm under load.

thanks , bikes had new coils and carb sonically cleaned , ignitech , carb rebuild, but the jerks at 5.5k are very forceful which is why I put it down to electrical fault rather than petrol fault
Maybe I should do the plug cap mod?

 

[Phil keen]

To the original OP
1. How do you know R cyl is too hot?
2. The clean plug shows no evidence of being too lean, 10 miles of use is too few to determine that.
3. The sooty plug definitely looks like it is a bit rich.
4. I suspect the issues at 5k revs are caused by one or both cylinders being too lean.
5. Tune the air-fuel ratio on each cylinder. There is plenty of info available about that depending on
Which model you have. A colortune could be handy, personally I didn’t get on too well with that so have just fiddled with settings based on feel and plugs. Then balance the carbs.
6. as sidecar Bob says, easier for all, especially you, if issues with bike kept in one thread. 👍🇬🇧
7. good luck - you have a running bike so solution probably not too far off.

Thanks for that , only reason I say that right cylinder is running hot is because the exhaust pipe gets too hot to hold a lot quicker than the left
As I said to someone on here I thought problem was electrical to make it jump/misfire at 5k revs and over but now I’m not too sure
Thanks

 

[murrayf]

what year is your bike?

 

[reclinedrelic]

In one of his other threads he says 1981 CX500 B Cx500 b 1981 misfires around 5000 revs

 

[Phil keen]

what year is your bike?

Hi it’s an 81
Cx500b

 

[Randall-in-Mpls]

Check that serial number against the list. You might have an earlier engine.
Or did the Standard use the "CX500-..." numbers all the way through the run?

 

[CXPHREAK]

CX500 right up to numbers starting at 24 in 1982.

 

[Sidecar Bob]

Hi it’s an 81
Cx500b

If you would take a few minutes to add your location and your bike's model and model year to your profile Murray wouldn't have had to ask and you wouldn't have had to reply.

 

[Phil keen]

If you would take a few minutes to add your location and your bike's model and model year to your profile Murray wouldn't have had to ask and you wouldn't have had to reply.

Quick update guys , bought some cheap orange coils for bike (as recommended by someone on this fantastic site) and now bike is running smooth as baby’s bum - thank you all 👍👍👍