Author Topic: '72 CB750 (Read 4600 times)

smccloud · « **on:** June 22, 2007, 07:08:04 PM »

Ok,
I've owned a '72 CB750 for 3 years now. It runs great, but has an oil lead on the left side of the engine by the side stand. I know I need to pull the engine out and at least re-ring it since I also need to put a new head gasket in it. The one thing that concerns me is the fact that I can't find points for it, anywhere. I also need four floats for it since #1 keeps absorbing gas and I keep having to tweak it. Anyone have a suggestion on where to find floats, and how to at least slow down the oil leak?

It sat for 10 years before I got it and the previous owner put a new seat/handle bars on it. I got the handle bars switched back, just need to get the seat done.

Here's my baby

Magpie · « **Reply #1 on:** June 22, 2007, 08:54:50 PM »

The oil leak may be the auto chain oiler adjusted wrong. It's a screw on the end of the countershaft where the drive sprocket is. Turning it in will slow to stop the flow of oil out of it. Worth a try.
Cliff..

gold01ca · « **Reply #2 on:** June 22, 2007, 09:33:00 PM »

oil seal on the transmisssion shifter possible source of oil leak.
lotsa 750 used carb sets on ebay, pretty cheap, might be an economical source for the floats you need plus other parts.

cheers!

smccloud · « **Reply #3 on:** June 23, 2007, 09:07:59 AM »

Quote from: gold01ca on June 22, 2007, 09:33:00 PM

oil seal on the transmisssion shifter possible source of oil leak.
lotsa 750 used carb sets on ebay, pretty cheap, might be an economical source for the floats you need plus other parts.

cheers!

i've replaced the shifter oil seal already, didn't help

i will look on ebay again for floats, although right now my bigger concern is pulling the engine to replace the gaskets in it...........

gold01ca · « **Reply #4 on:** June 23, 2007, 09:11:54 AM »

Quote from: smccloud on June 23, 2007, 09:07:59 AM

Quote from: gold01ca on June 22, 2007, 09:33:00 PM
oil seal on the transmisssion shifter possible source of oil leak.
lotsa 750 used carb sets on ebay, pretty cheap, might be an economical source for the floats you need plus other parts.

cheers!

i've replaced the shifter oil seal already, didn't help

i will look on ebay again for floats, although right now my bigger concern is pulling the engine to replace the gaskets in it...........

you might end up buying a set of used carbs just to get the floats

smccloud · « **Reply #5 on:** June 23, 2007, 09:35:20 AM »

Quote from: gold01ca on June 23, 2007, 09:11:54 AM

Quote from: smccloud on June 23, 2007, 09:07:59 AM
Quote from: gold01ca on June 22, 2007, 09:33:00 PM
oil seal on the transmisssion shifter possible source of oil leak.
lotsa 750 used carb sets on ebay, pretty cheap, might be an economical source for the floats you need plus other parts.

cheers!

i've replaced the shifter oil seal already, didn't help

i will look on ebay again for floats, although right now my bigger concern is pulling the engine to replace the gaskets in it...........

you might end up buying a set of used carbs just to get the floats

thats what i'm thinking. it runs fine for now.

HondaMan · « **Reply #6 on:** June 23, 2007, 01:05:18 PM »

That's a late K2 or K3, judging from the paint color and tank stripe.
I have the K2, also. The chain oiler came set too rich from the factory, which can generate the leaking oil down the sidestand. If you are diligent about lubing the chain yourself, you can turn the oiler in 2 turns to shut it off, like I do.

Points for these bikes are still available at Honda dealers, and all over the Web. Don't buy the ones fromm Daiichi, these are real cheap and wear very quickly. Use Hitachi, TEC or Denso points.

I build and sell an electronic box that runs from the points, switching the ignition coils with transistors. This makes the points last for many years without wear, it improves gas mileage, starting, and engine smoothness, making a little more power, and comes with a 5-year, no hassle warranty. If the electronics ever fail, you simply unplug the unit and plug your points back in and ride on, in about 5 minutes. Thus, it has electronics with a "backup plan" built in.

If you're interested in one, drop me a PM. Each one I sell generates $1 back to SOHC4.us to support this site, too!

smccloud · « **Reply #7 on:** June 23, 2007, 01:46:12 PM »

Quote from: HondaMan on June 23, 2007, 01:05:18 PM

That's a late K2 or K3, judging from the paint color and tank stripe.
I have the K2, also. The chain oiler came set too rich from the factory, which can generate the leaking oil down the sidestand. If you are diligent about lubing the chain yourself, you can turn the oiler in 2 turns to shut it off, like I do.

Points for these bikes are still available at Honda dealers, and all over the Web. Don't buy the ones fromm Daiichi, these are real cheap and wear very quickly. Use Hitachi, TEC or Denso points.

I build and sell an electronic box that runs from the points, switching the ignition coils with transistors. This makes the points last for many years without wear, it improves gas mileage, starting, and engine smoothness, making a little more power, and comes with a 5-year, no hassle warranty. If the electronics ever fail, you simply unplug the unit and plug your points back in and ride on, in about 5 minutes. Thus, it has electronics with a "backup plan" built in.

If you're interested in one, drop me a PM. Each one I sell generates $1 back to SOHC4.us to support this site, too!

that does sound interesting. if it is oil that is supposed to get to the chain, then i have a problem; like its doing the chain no good. i still have to lube it myself.

HondaMan · « **Reply #8 on:** June 23, 2007, 07:37:25 PM »

There's only a couple of things that can make an oil leak in that area:
1. Chain oiler
2. Bad (broken) countershaft seal.

There's a remote 3rd possibility, if the previous owner broke a chain on it, which is: the cases could be damaged inside that cover. If you pull off the countersprocket cover, this damage would be real obvious, though.

Under the engine, there are 2 things where leakage might occur (also rare):
1. The big gasket around the crankcase plate (this is where the oil pump mounts, in the middle of the bottom of the engine).
2. The neutral light's switch. This has a wire going to it, so it's easy to find, but can't be removed unless the engine is taken out.

smccloud · « **Reply #9 on:** June 24, 2007, 01:29:49 AM »

Quote from: HondaMan on June 23, 2007, 07:37:25 PM

There's only a couple of things that can make an oil leak in that area:
1. Chain oiler
2. Bad (broken) countershaft seal.

There's a remote 3rd possibility, if the previous owner broke a chain on it, which is: the cases could be damaged inside that cover. If you pull off the countersprocket cover, this damage would be real obvious, though.

Under the engine, there are 2 things where leakage might occur (also rare):
1. The big gasket around the crankcase plate (this is where the oil pump mounts, in the middle of the bottom of the engine).
2. The neutral light's switch. This has a wire going to it, so it's easy to find, but can't be removed unless the engine is taken out.

of the first three, it can only be #1, i've replaced the countershaft seal already, and no damage from a broken chain i can see. could be one of the last two, but to me the first one is the most probable.

HondaMan · « **Reply #10 on:** June 24, 2007, 10:44:55 AM »

Quote from: smccloud on June 24, 2007, 01:29:49 AM

of the first three, it can only be #1, i've replaced the countershaft seal already, and no damage from a broken chain i can see. could be one of the last two, but to me the first one is the most probable.

Um...how did you replace the countershaft seal without splitting the cases? Normally, this seal came with a bulge around the back edge that held it in, and it was impossible to install from the outside as a result. Has the seal design changed from that?

smccloud · « **Reply #11 on:** June 24, 2007, 10:55:31 AM »

Quote from: HondaMan on June 24, 2007, 10:44:55 AM

Quote from: smccloud on June 24, 2007, 01:29:49 AM

of the first three, it can only be #1, i've replaced the countershaft seal already, and no damage from a broken chain i can see. could be one of the last two, but to me the first one is the most probable.

Um...how did you replace the countershaft seal without splitting the cases? Normally, this seal came with a bulge around the back edge that held it in, and it was impossible to install from the outside as a result. Has the seal design changed from that?

ok, maybed i didn't. i am almost 100% positive i did but i could be wrong. i will be pulling the engine out this fall to rebuild it (and i hope i can afford a big bore kit, camshaft, etc) so i will know for sure then that it gets done.

smccloud · « **Reply #12 on:** June 24, 2007, 05:59:23 PM »

looking at the automagic oiler is out until i can get the bike to my "mechanic's" (read, dad's) to use his impact driver. plus i'm more concerned about having to run the high beam filiment (aimed lower) to have a low beam since the low beam filiment died on me today. also, is it normal for the tach to basically stop responding at 7500? mine started doing that. i know redline is 8 grand, but i'd like to know when i reach it. i plan to take some carb cleaner to the cable next weekend and then re-oil it, i'm just wondering if anyone has ideas on other things i should check.

nilsey · « **Reply #13 on:** June 24, 2007, 06:14:31 PM »

i think this same thing is happening on my 76 cb550k -- i am going to replace the oil seal where the shifter goes in, i thinks thats where oil is slowly seeping out.

it's not really bad enough at this point to be urgent....

smccloud · « **Reply #14 on:** June 24, 2007, 07:07:58 PM »

Quote from: nilsey on June 24, 2007, 06:14:31 PM

i think this same thing is happening on my 76 cb550k -- i am going to replace the oil seal where the shifter goes in, i thinks thats where oil is slowly seeping out.

it's not really bad enough at this point to be urgent....

i've replaced that seal already too.........

HondaMan · « **Reply #15 on:** June 25, 2007, 08:50:40 PM »

Quote from: smccloud on June 24, 2007, 05:59:23 PM

looking at the automagic oiler is out until i can get the bike to my "mechanic's" (read, dad's) to use his impact driver. plus i'm more concerned about having to run the high beam filiment (aimed lower) to have a low beam since the low beam filiment died on me today. also, is it normal for the tach to basically stop responding at 7500? mine started doing that. i know redline is 8 grand, but i'd like to know when i reach it. i plan to take some carb cleaner to the cable next weekend and then re-oil it, i'm just wondering if anyone has ideas on other things i should check.

If the bike's been sitting a long time, the tach cable can get "jerky" from hardened grease and oil inside. Try cleaning it out and oiling it, or get a new one. The uneven cable speed will make it read lower than normal RPM.

smccloud · « **Reply #16 on:** June 26, 2007, 06:12:46 PM »

Quote from: HondaMan on June 25, 2007, 08:50:40 PM

Quote from: smccloud on June 24, 2007, 05:59:23 PM
looking at the automagic oiler is out until i can get the bike to my "mechanic's" (read, dad's) to use his impact driver. plus i'm more concerned about having to run the high beam filiment (aimed lower) to have a low beam since the low beam filiment died on me today. also, is it normal for the tach to basically stop responding at 7500? mine started doing that. i know redline is 8 grand, but i'd like to know when i reach it. i plan to take some carb cleaner to the cable next weekend and then re-oil it, i'm just wondering if anyone has ideas on other things i should check.

If the bike's been sitting a long time, the tach cable can get "jerky" from hardened grease and oil inside. Try cleaning it out and oiling it, or get a new one. The uneven cable speed will make it read lower than normal RPM.

i will do that this weekend when i get home from north carolina. little bit of a trip back to mn right now

CBNJ74 · « **Reply #17 on:** October 03, 2011, 08:41:54 AM »

Did it end up being the auto oiler? I'm having a similar problem.

smccloud · « **Reply #18 on:** October 03, 2011, 08:54:22 AM »

From what I remember, yes.

CBNJ74 · « **Reply #19 on:** October 03, 2011, 10:02:51 AM »

Sorry I just realized this thread is 4 years old lol.

I'm hoping that's what it is.

News:

Author Topic: '72 CB750 (Read 4600 times)

gold01ca

gold01ca