Topic: CB650 Engine rattle

[Hareetmanni]

Hi. I bought a CB650z 1980 couple of moths back. It makes horrible noise from the camchain. Is it hard to replace. I have the head off right now and it has been in machining shop. Just got it back and was thinking of slapping it back on. BUT i just remembered the horrible camchain rattle. I adjusted it but the bike died due to carbs leaking so badly. Should i just replace it now when the engine in open. And how hard is it to replace it. I have a video of it but i have no clue if i can put them here.

[fizzlebottom]

You're all over the place here. Slow down and let's cover a few things.

• You adjusted the cam chain tensioner. What procedure did you use?
• The carbs leaking has nothing to do with the cam chain tension, so separate those issues.
• What prompted you to disassemble the top end?
• Have you ever had the bike running the way it is supposed to? If so, what changed?

I don't want to jump to conclusions that the chain needs to be replaced yet, only because that's a pretty uncommon remedy. Since you have the head off right now, you can inspect the tensioner slipper and guide and see if there is any damage. They crack and sometimes the sidewalls chip away.

As for the video, figure out a way to get it on youtube and link it here. Might be helpful to hear, but might not be.

[Hareetmanni]

So. The bike has been sitting from 2014. The previous owner got it started. It was rattling then. I got it home and adjusted the tensioner as said in hondas service manual. I think it got quieter. But im not sure becouse when it was running the carbs shat the bed and it was running like #$%*. The carbs were already leaking like faucets. I took the carbs off. Then i took the exhaust off and looked into the exhaust ports and they were so caked in carbon build up. I took the head off to see the valves and they were really badly carboned up. Sent that to a machining shop to be refurbished and here i am now. I think the cam chain was 44€ which isnt bad. But i want to know how hard is it to change it.

Oh and another reason was that the gaskets were shot also on the head. The bike hasnt seen alot of service in its life... And ill upload it to youtube and link it here.

Edit:

[fizzlebottom]

I've heard tale of folks who bought cam chains with a master link and successfully changed it without splitting the cases. This would involve disconnecting a link on the old chain, connecting the new chain to it, then turning the crankshaft forward until you've pulled the entire old chain out, disconnecting the old chain from the new, and linking the new chain back together with the master link. So long as you didn't let it go slack at all at the bottom, you haven't lost timing. You could also hypothetically do this with a non-master link chain, but it'd require a chain link press. Not the end of the world.

Here's a good thread detailing the procedure: http://hondacb650.com/viewtopic.php?t=8112

[Hareetmanni]

Thanks. Im thinking about changing the chain. For piece of mind.

[bryanj]

The 650 has a hy-vo cam chain which you dont get a soft link for, its endless so its a complete engine strip

[RAFster122s]

You would always want to change the tensioner and slipper if you are changing the chain...

Head gaskets are hard to find (Honda OEM)

[fizzlebottom]

You would always want to change the tensioner and slipper if you are changing the chain...

Head gaskets are hard to find (Honda OEM)

Unfortunately tensioner parts for the SOHC/4 CB650 are just about gone. No new units anywhere until someone digs through their warehouse and happens upon a stash. Even when they trickle onto eBay they're likely to have cracks. Unless someone starts fabbing them or finds something that manages to work from another bike, the cam chain slipper is one of a few parts that will be the death of the SOHC CB650. Put it in the list along with crankshaft bearings. Once they're gone, they're gone.

[Tracksnblades1]

That’s coming from the camshaft chain…?

I would think you could feel where that’s coming from….

[Hareetmanni]

Somewhere from the middle of the cylinders. I think it got quieter when i adjusted it. But the bike ran horribly so i started to tear it apart. Carburators were shot. And i have cleaned the now but i cant put them together anymore. Really starting to irritate this bike.

[fizzlebottom]

Somewhere from the middle of the cylinders. I think it got quieter when i adjusted it. But the bike ran horribly so i started to tear it apart. Carburators were shot. And i have cleaned the now but i cant put them together anymore. Really starting to irritate this bike.

Your carbs are not shot. They were probably dirty as hell and maybe had some rotted rubber bits.

What part of reassembly are you stuck on? Everyone talks about how complicated these carbs are and how much of a nightmare they are to work on, but I think the majority of that difficulty comes from people who lack patience and don't use the right tools for the right job.

How far did you go tearing them apart? Are they completely separated? If so, the only difficult part is going to be getting that choke return spring back in correctly.

Give some more details on what's going on and we might be able to help.

[Hareetmanni]

Hi. Its been a while. So im at the part where the carbs are together. I had them seperated and fully cleaned them. They were coaated with slime from gasoline. Anyways i got the carbs and springs back. BUT the choke spring and the whole choke assembly is still not back together. When i twist the. "throttle" the carbs are now really tight to move. And when i put the flange that keeps them together the carbs throttle wont move. The carbs have been off the bike now for like 2-3months. And im seriously thinking of ripping the carbs off my other 650 and buy a set of mikunis for it from Murrays Carbs. It a 900€ investment but aleast they will be better for my other 650 bcs it has 4-1 exhaust. And most importantly way easier to work on. This project has been hell...

[fizzlebottom]

When you reassembled the carbs, did you follow instructions in the FSM or just reverse your disassembly steps? There aren't great written instructions on how to reassemble the choke spring in the manual, so following this video (

and reading this document (https://www.cb750c.com/publicdocs/SeanG/Honda_Carb_Manual_revG.pdf) are required to properly do it.

The throttle tightness sounds like you either replaced the felt seals with rubber o-rings, which is wrong, or your carbs are not aligned to each other properly. You need to install the two brackets with the carbs on a FLAT surface, so they're aligned. If you don't, the throttle and choke shafts can bind badly.

All in all, it sounds like you're rushing a lot or not following instructions. If your carbs are not physically damaged, they're perfectly fine and just need to be reassembled and sync'd properly to work. Don't spend the money on new carbs until something is irreparably broken or damaged.

[Hareetmanni]

Havent found mutch info on these carbs on the internet. I have the haynes book but its pretty mutch useless. The pics arent the best and its not full on dissassembly. Thanks for the video. I was putting the rear wheel back on the bike but i noticed the Crown nut for the rear axle was stripped. I have no clue how that even happened but now i have to go hunt for a new one. Parts arent easy to find here. When i go to a honda dealer they cant find the model anywhere. Not even with the serial number. And i have to rush the bike to get on a rideable state in order to get it to my name and insured. Should have just go to the Mot with leaking carbs and bent forks. Atleast id have it on my name. But next time i know atleast.