• Enter the March CB750 Supply gift certificate giveaway! It's easy... Click here, post something, and you're entered into the drawing!

Crudiest mess Ive ever seen

JBW5

CB750 Member
Messages
17
Reaction score
0
Points
1
Location
Hot Springs Arkansas
Just broke into my 78 cb750s carbs and they are crusty and nasty! What is the best way to thoroughly clean these bad boys? What are yalls thoughts on rebuild kits? There seems to be mixed feelings on this! This is my first motorcycle so I am new to this world. I know I need new rubber but what about the brass parts? Thanks!
 
I think the best way to clean them is to buy the set I just posted on ebay, and work on other things. mine are clean and ready to run. sell yours to the next guy let him fight with gunk.
 
nope it don't. several hours work and most of them can be used. which is my point. the value of his good but gunked set subtracted from my nice clean ones, is less money then 3-4 hours work taken away from other things on the bike. And god knows whats in those idle passages.
 
Cyclebuster, what are you asking just curious? I'm cheap myself but I dug into these things tonight and they are crusty white? The holes seem to be clear and I have rn the bike with them in this condition but it was rough. I have never seen a caeb that looks like this? What is this gunk and can it be reversed? Thanks!
 
not in my experience. the aluminum is corroded from water. usually they fall apart. all aluminum turns white, but it gets really bad and there is no hope. usually the float pins bust off, but the first sign is usually all the float bowls will get pinholes. sets with "need cleaned" and no picture of the inside. those are generally in the $70-100 dollar range, and you gained nothing. super nice sets run into $2-300 plus shipping. I am asking $150 shipped to your door. Mine will drop on and run. The man I got these from paid $150 last year for them.
http://www.ebay.com/itm/151012220139?ssPageName=STRK:MESELX:IT&_trksid=p3984.m1555.l2649

I can do these for $125 off ebay
 
Last edited:
What all can i take apart on these things? Is it important to dig into the top end or what? Top doesn't look bad but iI want to break this thing down and scrub on it extensively! Any good diagrams out there or threads on this topic? What pieces need to be cleaned for functionality? Thanks! Sorry for all the questions. carb1.jpgcarb2.jpgcarb3.jpg
 
don't mess with the tops they should be tuned with the engine. just lube them, scrub the bottom fuel area clean, clean the jets and make sure the small jet is open.
 
Once you get it back together an running you should sync. the carbs because you have no idea how close there were before. Checking carb sync is a periodic maintenance check/adjust anyway. Things do wear, things do get out of adjustment and should be checked as part of your maintenance routine.

On these carbs one of the biggest problems will be to get the accel pump check balls to work correctly especially with that amount of corrosion. The one in the accel pump cover in particular is hard to get to work because it is in the very bottom and gets stuck and hard to get cleaned out. I have had to repeated soak and blow through the passages to get the check ball to free up. If you dont get the accel pump check balls to work you will end up with a bad stumble and hesitation off idle.
 
do you know of anything that can stop that carb destruction once they go white? my triumph carb needs to be scrubbed 3-4 times a year and its all from the white death.
 
You know I have never had a problem with any of my carbs. I am really beginning to believe it is a result of the different gasoline people get in different parts of the country. Our low grade and our premium are 100% gasoline with no ethanol. I also never drain my fuel bowls and keep the carbs full all the time. I do drain the bowl and then turn the petcock on every month or so to get fresh fuel in. The only carbs I have gotten with the corrosion are ones I bought for pieces and they always seem to come off the coast or southern region.

Also just for some information I have read about. Methyl alcohol and alkali in gasoline are big if not the biggest contributors besides large amounts of water to aluminum oxidation. I was an auto tech for years and have dealt with factory rebuilt automotive carbs. What I learned was that carb re-manufacturing companies take the carb bodies and tumble them with some sort of media to remove all oxidation. They then Chromate all the parts to keep the corrosion from reappearing. Many times the carbs also came with instructions to stay away from ethanol fuels and certain off the shelf fuel additives because of the risk of corrosion. Dont get me started on the ethanol debate!
 
I am an ethanol enemy. I studied alternative fuels in college 30 yrs ago. it was less feasible back then. now we are starving the world with our corn prices.
 
I hate it too. I have seen the effects of ethanol on fuel systems. I dont care what the supporters say it causes problems. There is a reason why E85 vehicles have to have stainless steel tanks, lines, etc, as well as ethanol approved gaskets and rubber pieces. OK enough of the ethanol talk lol.
 
Thanks for the advice! I am thinking trying a pine sole soak! Has anyone done this? Also does anyone have a link to a fsm manual for a 78 cb750? I have seen one online but cant find it now....I have takin out all the brass in the bottom. is that all i need to do before the dip? Is there any reason not to leave them all racked? Thanks for the help! carb4.jpg
 
Thanks for the info! So should I break it down further? Essentially the jets being clean is the main thing right? How spotless do the bowls really need to be? Just in case the soak and scrub doesnt get it all off. Thanks
 
just as long as there are no loose particles, they can actually look like hell. yours aren't gummed. scrub the inside of the fuel compartments clean, verify all the passages in the jet holders are clean, verify the idle jets are open, and the float valves work, it should run fine.
 
Back
Top