Topic: exhaust temp lean/rich im a noob

[thumperxes]

im a noob but have mechanical skills im looking for advice done a lot of research but still need to learn from asking questions.  what i have is popping coming from what i can tell from the #2 exhaust possibly #1, but believe #2.  what i have with the exhaust temp is 3 and 4 seem like what would normal be but #2 is definitely hotter than 3 and 4 but number 1 is much cooler than the rest. right now the exhaust is open drag pipes soon to be motogpwerks,  jets are 120s don't know if i should re jet or OK with this so far.

CB750K3
1) 3 and 4 exhaust temp seem normal not to hot
2) 2 exhaust is much hotter
3) 1 exhaust is cooler than all others
4) jets 120s
5) a/f adjusted to 3/4 out was at 1 out
6) i know i should do a complete carb rebuild but deciding on that or new carbs (would be months away from that though)
7)done carb sync all close to equal

looking for advice any would be appreciated don't want to take to mechanic rather learn from friends if i forgot something ask i will answer the best i can

[DJ_AX]

Welcome to the forum. Unless you've got a SOHC4 expert in your area, you are your best mechanic.
There are a quite few experts here on this forum!

Did you do the complete 3k tune up? ... in order? ... it matters a lot.
The carb sync really only matters after the other things; cam chain tension, valve lash, timing/dwell, filters, etc.

Is the popping on decel? That would indicate exhaust gasket leaks... no? Timing then maybe.

And to #6 ... yes... but you can at least make sure every orifice is spotless!

I'm sure others here will chime in...
Admittedly, I am not an expert

[thumperxes]

I have done new points, timing adjustment, plugs look ok but never been good at reading them, adjusted valve clearance (a few were out of spec),


need to check cam chain tensioner

do plugs 1 and 4 and 2 and 3 fire at the same time in pairs

[flybox1]

Did you do a bench sync, or a full vacuum sync?
All your air fuel.mixture screws set the same?

[lucky]

im a noob but have mechanical skills im looking for advice done a lot of research but still need to learn from asking questions.  what i have is popping coming from what i can tell from the #2 exhaust possibly #1, but believe #2.  what i have with the exhaust temp is 3 and 4 seem like what would normal be but #2 is definitely hotter than 3 and 4 but number 1 is much cooler than the rest. right now the exhaust is open drag pipes soon to be motogpwerks,  jets are 120s don't know if i should re jet or OK with this so far.

CB750K3
1) 3 and 4 exhaust temp seem normal not to hot
2) 2 exhaust is much hotter
3) 1 exhaust is cooler than all others
4) jets 120s
5) a/f adjusted to 3/4 out was at 1 out
6) i know i should do a complete carb rebuild but deciding on that or new carbs (would be months away from that though)
7)done carb sync all close to equal

looking for advice any would be appreciated don't want to take to mechanic rather learn from friends if i forgot something ask i will answer the best i can

There is no way to help you without knowing which carbs you have.
What year is the bike and what are the numbers stamped on the cars?
For all I know the #120 main jets are standard size.

Also all mixture screws need to be turned out to the correct amount and all 4 carbs need to be set the same amount.

Tell us what carbs and year we are talking about, THEN we can talk about it. Also need to know if you have the stock air filter system or aftermarket style parts?

[thumperxes]

the air filter are cheep pod type by standard (its stamped on the end) bike is 1973 k750 i believe stock carbs, i cant seem to see any numbers on them but i have a pic of the carbs attached

[lucky]

the air filter are cheep pod type by standard (its stamped on the end) bike is 1973 k750 i believe stock carbs, i cant seem to see any numbers on them but i have a pic of the carbs attached

We will have to know if they are 7A's or 657A's.

There is a number stamped on them, and you will have to find it even if it means wiping some dirt or burned on fuel off of the carb.

CLICK on photo for a larger version.

[thumperxes]

657A and next to that or after that LA9?

[thumperxes]

also what clip position should the needle jets be set at right now one and two are at second from the bottom. my floats were off #1 was 1.055 now 1.023 and #2 was .965 now 1.023, havent got to carb 3 or 4 yet, also think i found my idle jet (40) on 1 was clogged but now clean.

[ekpent]

  Have you ever had the carbs off the bike yet for a good cleaning yet since you have owned it,if not its probably time.Don't need new stuff just good clean components. You can eliminate a lot of variable and guesswork by doing that first. Getting the proper size fuel line and routing it correctly also helps along with a nice clean tank.