Topic: Trixie - 1977 CB750K - Project

[BrockSamson]

Still wondering about the key question.

I did find out the gauges are supposed to light up and found a wiring diagram.  It looks like I am going to have the check the bulbs and connectors.  I will update on that later.

Also, if you look in the for sale section I am selling my VM29 smoothies if anyone is interested.

Also, I have always loved the bikes that relocate/hide the oil tank into the gas tank.  I was surfing the interwebs and found this and fell in love:

http://benjiescaferacer.com/convkit-750-sohc.php

The SS Dimpol with integrated oil tank.  Beautiful.  This would be a next winter item when I tear down the bike.  If I was to get that I would most certainly need to relocate the battery and probably get a lithium ion battery.  I wonder where I could hide that guy...

[BrockSamson]

Opened up my speedo and tach last night.  Found a couple bug shells and a total of 4 blown bulbs.  Changed those out and I am good to go!    .  Very happy it was not a wiring issue.

I also put back on the left side cover and I need to drill and fit the right one.  I have those plastic replacements you can find all over the place.  The left one was a big urgent because that oil tank can get a bit hot against my leg. haha.

Next up:

Cheaply fixing the paint mess on my tank, seat and side covers.  Probably going to stick with flat black for the riding season.

[BrockSamson]

Ha, starting to feel like I am talking to myself but that is fine. 

I rode the bike for the first ride of any significant distance.  I noticed a few things:

1) Sometimes the throttle isn't as responsive as I like initially.  This is probably because the rebuilt accelerator pump has clogged holes or the holes need to be widened.  I will be opening it up soon enough.

2) At higher RPMs the bike can be a big unresponsive and boggy.  I think I am going to need larger main jets.  I have what I believe is a MAC brand 4 into 1, stock airbox with new K&N.

3) After the ride I park the bike and noticed for the first time that the idle is 1k higher than when I left!  I am running 1/3 can of seafoam in this full tank of gas.  I am not sure if that had something to do with it... but what would cause the idle to change like that? 

[Boulevard_beck]

I don't think I can help too much - you seem to know a lot more about bikes than I do - but, I'm along for the ride to learn a thing or two for my own 78 750k build.

Also, you kinda confirmed my decision to stick with the stock airbox, too. Too bad, because not only did I already purchase pod filters, but they look so much cooler than riding around with a suitcase stuck between my legs

[BrockSamson]

Yeah learn from my mistakes!  haha.

I like the pod filters because it cleans up everything behind the carbs and makes taking everything out that much easier. 

You have probably already seen this said... but after doing it so many times taking the airbox, carbs, throttle and choke cables out it becomes second nature.  I am about to have to pull everything again to check the accelerator pump. 

All the horror stories of tuning, leg position, etc of dealing with pod filters is just not worth it to me.  If I was to get rid of the airbox I would get the anti-pod that tintop offers.  But, that still wouldn't be a problem free solution to removing an airbox but far better than pods.

[BrockSamson]

Need a sanity check:

Quick update of what I am running:
1977 750K
PD41A Carbs stock specifications
Stock Airbox with new K&N filter
4 into 1 exhaust.
Timing, points and all that jazz has been set.

Took the bike out today to confirm my suspicions that the accelerator pump might be bad.  Well it is definitely not bad... I think I had myself convinced they were because of the bogging down above 40-50% throttle I just had never singled them out.  In all gears I can flip the throttle back and it goes.  There is no delay.  So that is good, not sure why I wanted to blame the accelerator pump for a problem going above 40-50% throttle.

So the bike is bogging down I wanted to give it 100 miles of seafoam treated gas before I pulled them back out.  The obvious answer for me would be main jets.  Although I realize that isn't the easiest of answers.  I was going to try to accelerate with the 50% throttle and as it struggled I was going to pull the choke and test.  I made one attempt at this and wasn't comfortable accelerating, taking my eyes off the road and trying to screw around with the choke.  I also know my apartment neighbors would hate me if I was out in the parking lot at 50% throttle. 

So here are the next steps I am going to take after work tomorrow:
1) Pull all of the plugs.  Take picture and post here.
2) If there is no sign of fouled plugs and they do in fact look lean... I am thinking of getting new idle and main jets.  Looking at this thread I might want a similar setup to Lucky:
http://forums.sohc4.net/index.php?topic=106060.msg1194522#msg1194522
#42 idle
#120 main

I will be posting my mixture screw setting soon.  I don't remember off hand.

[BrockSamson]

Put the new petcock and 120 main jets in (decided to leave the idle jets alone)...

SHE RUNS SO WELL!  It is like night and day.  I have a huge smile on my face from my last ride still. 

[BrockSamson]

My project tonight/tomorrow night is to sand and paint my new plastic side covers.  I am using Dupli Color truck bed liner based on a few suggestions here on the forums.  I heard there were great results.  I like the idea of have a resilient paint that will last just fine through the riding season.

After that will be the seat, then hardest of all fixing the tank which still looks a mess. 

I will be sure to post pictures.

[BrockSamson]

I am lacking pictures but the bed liner came out great on everything except the tank.  There were a couple runs and I am going to have to sand and repaint.  I will post pictures tonight... after I see what is wrong with the bike... I ran into an issue

Drove the bike in the rain last night.  It was a heavy downpour.  The bike was sputtering and almost seemed to behave like it had an intermittent air leak.  I am assuming this is because there was an exposed electrical connection that was shorting?  I have no idea.  Any have experience with this?

Also, my clutch is slipping more and more... it is going to be time for new clutch plates I think.

[BrockSamson]

I am thinking of getting the CycleX Super Clutch Kit. 

I have the "Honda CB750 SOHC CB 750 Service Repair Shop Manual 1969-78".

On 4-2 it shows the clutch repair procedure but the transmission isn't in a bike frame.  My question is, will I be able to repair the clutch with everything in the frame?  Is it as straight forward as it seems?  I t looks like I should have no issue taking this on myself... am I correct?

[lucky]

I am leaning more and more towards the stock carbs.  Just opened one up and they have 115 mains.  As I examine them I get the impression that they were rebuilt recently...

When I see blue or red silicone i know a beginner has been working on it and I suspect problems.

[70CB750]

I didnt read it all, sorry, but could the clutch be just oil issue?  Seems low on miles to be worn out. Wild shot nothing else.

Anyway, are you legal and on the road? Godzilla will be here in September, you should sign up. Where in VA are you?

[BrockSamson]

yeah I am suspecting the oil being the issue too.  I am going to change it out with Rotella T soon and see how that fixes it.  After the bike is fully warmed up it grabs much better.

I am fully legal and on the road.  I am in Leesburg about 45min outside of DC.  I will definitely look into Godzilla (not sure what this is yet, haha!).

[70CB750]

I worked at AOL - Dulles for many years and we live near Warrenton. 
I am sure we will meet on the road some day

[BrockSamson]

I work right next to the AOL buildings.  I go to that Wegmans shopping center for lunch all the time. 

I have only seen one ratty 80s DOHC 750... not a single SOHC-4 yet.

[BrockSamson]

Question:

I want to pull my headers this weekend and wrap them.  I sprayed some liquid wrench and I am going to let that do its job.  Am I going to need a new set of these:

Exhaust Port Gaskets (Pk./4)-OEM Ref. #18291-254-000, 18291-MM5-860



Also, any words of caution or advice before I undertake this?  Thanks!

[70CB750]

When I put my new-to-me Mac headers on, I used new set of those. It is highly recommended.
Tape your frame to keep it from scratching. To remove the old one, impact screwdrivr - $25 at Sears is very handy.

[flybox1]

if you dont have them already, get  a set( of studs before you remount it....
http://www.partsnmore.com/parts/honda/cb750/?filters%5Bcategory%5D=hardware&filters%5Bfitting%5D=universal&filters%5Bper_page%5D=25

[BrockSamson]

flybox thanks a lot.  I am going to swing by sears and get a manual impact screw driver.

Other than the studs is there any other hardware you would suggest replacing?  If I had Hondamans book sitting in front of me right now I would just take a look at that, but I am at work.

I also have a new set of exhaust gaskets sitting in my cart.

[BrockSamson]

Well, my tach cable was leaking oil around the crimped metal piece on it.  So I went and bought Teflon tape, rubber insulating tape and zip ties.  I patched the cable and bam oil gone... so I thought.

I ride my bike into work this morning and I park it and see oil in new places.  I examine the cable and it looks fine... I follow the cable up and I find the source.. the oil instead of exiting out the bottom of the cable has flowed up into the tach and is now leaking out of there.   

Did some searching here and came to the conclusion I need a new tach cable seal and I will be using the wood screw method of pulling the old one out and tapping it back in with a socket just as has been suggested.

I have to say, haven't seen a single thread where the oil traveled all the way back up through the cable.  Is there a reason that there would be that much pressure?  If my crankcase vent tube has a bind in it would it cause pressure to increase in the engine?

[BrockSamson]

I am reading about crankcase pressure build up and I am thinking before I start the engine again I should either unbind the hose (if it has a bind) or just cut it if needed.  I should not be running the bike with any sort of blockage in the vent line.

[BrockSamson]

Word of advice, avoid the ignition from http://www.vintagecb750.com/.  Up until now I have had a great experience with vintagecb750 so this isn't so much a bash on them... but the ignition just about stranded me at the grocery store on my lunch break. 

I put the key in go to turn it and nothing is catching.  Spent about 5 minutes trying to get the thing to grab onto something inside the cylinder hoping I could nudge it into the on position... no luck.  I finally reached my hand back behind it and pushed up and turned the key and finally got it to turn on.  It looks like the back end is falling out... I am going to have to pull it out to get a better idea of whats going on.

Anyone have any sources for a solid well built ignition.  I don't mind it being expensive if it works... also... Has anyone just rigged up a 3 position switch and removed the key all together? 

[Boulevard_beck]

I was actually thinking of purchasing one of those ignitions because I only have one key and the original is a little "sticky". Maybe I'll hold off for now...

I remember hearing that someone removed their ignition all together and just used their relocated kill switch that was hidden under the tank near the carbs. I couldn't find the thread, but there was no other explanation on how they did it.

I'll keep an eye on what you decide on doing. I'm always interested in creative new ways to modify my bike to be a little more unique. As long as no one can uniquely just hop on my bike and take off with it

[BrockSamson]

Ha!  yeah I wouldn't recommend that product.  You can get a new key made or find a new key on ebay sometimes... but that was just as expensive as getting an entirely new ignition, so it seemed like a good idea.

I completely lost my only key so I had no choice.  If I can't repair the ignition I am thinking I might put in a hidden switch, but I will do my research first.  This just stacks onto the work I am doing tonight:

-Oil Change
-Spark plug change
-Putting in new pilot jets
-Removing exhaust to wrap and then installing with new exhaust O-Rings
-Find a new route for my engine vent tube
-Adjust clutch to improve my slippage problem.

The clutch slip is becoming unmanageable so hopefully new oil and the clutch adjustment are going to improve things.  Otherwise I have to pull the basket and measure springs and plates . 

I also really want to get the pilot jets in and see how the bike runs and check the plugs so I can report to Lucky, I know he is generating a database and I want to pass along good information to him.

[BrockSamson]

Update:

What I got to this last weekend:
-Changed oil with Rotella T
-Changed oil filter (keeping that stupid oil filter gasket on while getting the filter back on is a pain in the ass
-Changed spark plugs (which looked fantastic btw)
-Removed exhaust, I actually had studs and not the collars.  I am not sure how I feel about that... but the exhaust came off without much of an issue.  I wrapped the header mostly.  I ran out of wrap at the #3 and #4 pipes and a very small part of #2.  I got 45ft... but it just wasn't enough.  I went to Advanced autoparts to buy a roll of overpriced DEI black header wrap but they only had the white.  So I came back and bolted up the exhaust, when I was doing this I realized that there were never any exhaust gaskets installed.  Which is odd, right?  Well I installed the gaskets and bolted the header back up.  Started her up and after a lot of smoking from the liquid wrench and the wet header wrap I took her for a ride.  As usual the bike engine runs just fine but the clutch was still slipping.
-Adjusted clutch.  I took off the kickstand and popped the clutch adjustment cover.  I didn't have to do much there so focused on fine-tuning at the clutch lever.  I was able to get the clutch to not slip between 0%-75% throttle.  Which is a huge improvement.  I think a little more fine tuning and I might be good to go.  I also noticed no debris in the oil.  Which was run through a funnel with a filter so I could catch any junk that might be in there.  So I think the clutch plates are intact.  If I can not resolve the clutch slippage with more adjustment I am going to pull the plates and measure.

Another note:
The bike was running great and clutch was grabbing for the most part on the way home.  So I was running her pretty hard.  At the last stretch before my apartment I got her up to 80 (It is a 65mph zone and there was no traffic) and I got her there from a rolling start in 2nd gear and went about 60-75% throttle.  When I hit the turnoff I was down shifting and I was lightly on the brakes.  All of a sudden I started hearing a ticking and the exhaust note changed.  Then when I pulled in the clutch the bike died.  Well I was able to coast to the light.  I pulled the bike to the side and took a look.  Nothing was obviously wrong.  I pop the fuel tank and notice that there isn't much fuel so I switch to reserve.  I try to start it... no go... it kinda gets going but struggles.  So I try one more time with choke and trying to keep her alive with throttle... which works long enough to get to the next light.  At the next light it dies and I can't get her going again no matter what.

So I am sitting at the light, and right next to my apartment is a "public safety center" which is a combination EMS, Fire and Police station.  So I figured I could just walk my bike across the street and to the safety center.  Well outside of the safety center are two EMS and two cops.  They are watching me.  Mean while the damn turn signal for the turn lane will not activate because I am on a motorcycle so I have to wave down traffic to stop and let me walk across with the bike.  During all of this the cops do not put in any effort to even look like they are going to give me a hand at getting through traffic.  Thanks for the public service...

So I get my bike across the street.  I screw around with the bike not really being able to identify what is wrong and decide to just sit there and let her cool down enough to safely get the wrench in my bag around the exhaust studs to see if they are tight still.  Well I check and they are fine.  I try to start the bike again and it gets going but struggles.  I am able to get her to my parking spot < 1/4 mile away.  Well I park it and wait for it to cool down fully.  I start the bike 3-ish hours later and she starts up just fine and idles well.  I decide to make a run to the gas station which is <1 mile away.  I get on the bike and she gets there without issue and runs fine.  I fill it up with gas and cruise around for 4-5 miles and there are no problems. 

My theories as to what happened... I recently bought a new petcock.  I think there is something wrong with the operation of "On/Off/Reserve".  The bike should operate appropriately once I switched it to reserve.  The bike had been running in the "On" position.  So either the reserve is not operating correctly or the petcock is backwards and "on" is the reserve?  I am not sure.  Also... why would the bike operate fine after a full cool down on the way to the gas station?  It had the same amount of fuel as when it had died.  Well that got me thinking... before I left my buddies garage where I was working on my bike I dumped in about 1/8 a bottle of seafoam just for the heck of it and because I had some left.  Well with very little gas in the tank and that much sea foam I might have overdone it.  But, I would still be operating on that highly concentrated bit of gas to the gas station where it ran fine.  Finally, I am starting to wonder if when the bike is at its hottest that is when an exhaust leak is occurring and when the bike is cooler and at a lower temperature the exhaust leak occurs.

More testing is needed that is for sure.  Right now I am hoping I can just say it was because of the very low amount of fuel in the tank.

Todo:
-Adjust clutch further
-Finish wrapping header and put the DEI protective spray on.
-Put in and test new pilot jets