1971 cl100

teazer

Well-Known Member
DTT BOTM WINNER
As the two bolts are tightened, they bow the mating surface. The torque setting for the carb flange is quite low.

When you take the carb off, remove the O ring and check it across the flange with a straightedge (steel ruler) or on a surface plate. No gasket needed if there's an O ring and replace the O ring with a new OEM one - not from the plumbing section of the hardware store.

You could also replcae the two nuts with Fuji or nylock nuts.
 

benroloff

Member
As the two bolts are tightened, they bow the mating surface. The torque setting for the carb flange is quite low.

When you take the carb off, remove the O ring and check it across the flange with a straightedge (steel ruler) or on a surface plate. No gasket needed if there's an O ring and replace the O ring with a new OEM one - not from the plumbing section of the hardware store.

You could also replcae the two nuts with Fuji or nylock nuts.
I put a new oem o-ring on but I get the feeling that I have been tightening the carb way to tight. I never would have thought of something like that being a problem. I will put a straight edge (surface plate is wishful thinking for me lol) on it just to be safe too. Thanks!
 

whynot

~~~If it ain't raining, I'm riding~~{iii}?~~prost~
Never heard of something like that. Do you know the reason behind that?
Not sure, but it seemed to cause it to bulge out in the middle.

When I loosened them it seemed to run a little better.
 

teazer

Well-Known Member
DTT BOTM WINNER
Get a piece of thick glass and stick a sheet of wet and dry on it and carefully rub the carb on that to get it flat. use some WD40 or even water to make that easier and keeps the wet and dry from clogging as fast. You will see a new shiny bit at the ends where it was rubbed down appear quickly. You want it completely flat.

push carefully to avoid it rocking and ending up worse than when you started.

You could probably put teh carb in a lathe or mill, but I don't have either of those and i can clean up a flange in less time than it would take to drive to the guy that does my machining.
 
Great tips.

Because of the o-ring question, I still wonder if the insulator is on the correct side of the manifold and both gaskets are installed.
 

teazer

Well-Known Member
DTT BOTM WINNER
Not familiar enough with that specific bike, but rarely do they have a gasket plus an O ring. Honda used to refer O rings
 
On the 100/125 bikes it goes like this: the carb mounts to the manifold (sandwiching the o-ring in-between), then there's a paper gasket, followed by a plastic insulator, then another paper gasket, then the head.

 

pidjones

Well-Known Member
If you do the glass and sandpaper, a real quick way to check flatness and see high spots is to color the surface with Sharpie (us old timers use Dykem Blue) and do a quick sand - that will take color off high spots that you need to bring down.
 

teazer

Well-Known Member
DTT BOTM WINNER
Good tip. I use sharpie.... And repeat for both sides of the insulators and that spacer.
 

benroloff

Member
Thanks all for the tips guys. I loosened the carb nuts off and that helped a ton. It still has some occasional issues, so I’ll get the carb pulled off one of these days and check flatness. Other than that the bike is coming together. I’ve got new front brake shoes coming in soon so that should be nice. Does anyone have a good way to lube these cables? They don’t seem to come apart as far as most modern cables so I can’t seem to find a way to get any cleaner or lubricant in them
 

benroloff

Member
So I finally got a day to work on the bike again and when I put a straight edge on the carb flange it was definitely warped so it i got that all flattened out and did the spacer and insulator for good measure too. I also went and bought some gasket material and cut some new gaskets. The old ones were falling apart and the spacer was actually backwards so there was one gasket between the insulator and the head, none between the spacer and insulator, and then the o-ring and the other gasket between carb and spacer, so that was definitely wrong and not helping things. The bike doesn’t seem to want to run away at idle anymore so I think that should be fixed. Unfortunately when I had the carb off I noticed that the brand new floats that I bought already leak, and when I contacted the seller I got an email response saying that they are “out of office” until the end of the month, so that’s just awesome. I was able to drain them though and solder up the hole and they seem to be holding now, but I’d still rather have brand new ones that I didn’t have to be resealed.
 

benroloff

Member
Oh I almost forgot about my dummy of the year award. So when I removed all the old gaskets I had to remove some residue from the mating surfaces, and I put a paper shop towel in the intake port on the head so that I wouldn’t drop a bunch of seal material down into the engine, but as it would turn out I forgot to take it out when I reassembled everything. So basically the bike started right up with no issues but when I revved it it violently died and I spent hours trying to find the problem and cleaning the carb and checking spark and timing before I took the carb off and looked down the intake port and realized what I had done. Thankfully I was able to fish it all out except maybe a few tiny little pieces that I could smell burning off when I got the bike fired up. So hopefully I didn’t do any serious damage to the engine when the remnants of the paper towel got sucked down cause man would this really blow.

TL: DR
I am a moron
 

whynot

~~~If it ain't raining, I'm riding~~{iii}?~~prost~
Oh I almost forgot about my dummy of the year award. So when I removed all the old gaskets I had to remove some residue from the mating surfaces, and I put a paper shop towel in the intake port on the head so that I wouldn’t drop a bunch of seal material down into the engine, but as it would turn out I forgot to take it out when I reassembled everything. So basically the bike started right up with no issues but when I revved it it violently died and I spent hours trying to find the problem and cleaning the carb and checking spark and timing before I took the carb off and looked down the intake port and realized what I had done. Thankfully I was able to fish it all out except maybe a few tiny little pieces that I could smell burning off when I got the bike fired up. So hopefully I didn’t do any serious damage to the engine when the remnants of the paper towel got sucked down cause man would this really blow.

TL: DR
I am a moron

Sounds like something I would do, and on more than one occasion.

I don't mean to laugh at you......just with you.

That's funny right there, I don't care who you are.......o_O

I think paper towels are bio-degradable, so you should be ok, I think
 

Luugo86

'73 CB350, '78 XS650 Cafe Killer
Oh I almost forgot about my dummy of the year award. So when I removed all the old gaskets I had to remove some residue from the mating surfaces, and I put a paper shop towel in the intake port on the head so that I wouldn’t drop a bunch of seal material down into the engine, but as it would turn out I forgot to take it out when I reassembled everything. So basically the bike started right up with no issues but when I revved it it violently died and I spent hours trying to find the problem and cleaning the carb and checking spark and timing before I took the carb off and looked down the intake port and realized what I had done. Thankfully I was able to fish it all out except maybe a few tiny little pieces that I could smell burning off when I got the bike fired up. So hopefully I didn’t do any serious damage to the engine when the remnants of the paper towel got sucked down cause man would this really blow.

TL: DR
I am a moron
Haha... that's like your bike building initiation dude... I've done some real bonehead stuff that cost me a lot of time and effort... glad you caught it tho, now you have SUPER clean carbs xD
 

Luugo86

'73 CB350, '78 XS650 Cafe Killer
Also I'm really interested to see what you do here... I really like the small displacement metric bikes.. they are 2 tons of fun in a 10lb bag
 

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