Intake manifold question.

[Zonie]

My new to me 76 XS needed new carb holders / manifolds which I have just gotten. Looking at them there are marking L & R so I know they are sided. Then I noticed that they are tapered with one side thicker than the other, so which way do they go? Thick to the inside or outside?

 

[Jim]

The engine is tilted forward ever so slightly. The thin edge goes on the bottom to bring the carbs back to level.

 

[Zonie]

The engine is tilted forward ever so slightly. The thin edge goes on the bottom to bring the carbs back to level.

When I look at them it "looks" to be thicker side to side? I will go back out to the workshop and look at them again and take pictures too.
Thanks for your help.

 

[Jim]

They bolt in at an approx. 45° angle. So the top inboard is the thickest part.

 

[Zonie]

Well I made a quick trip out to the workshop and took a couple of pictures. I see what you are talking about Thank you one more problem solved.

 

[Zonie]

They bolt in at an approx. 45° angle. So the top inboard is the thickest part.


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Those pictures are great, Thank you.

 

[Zonie]

Well I have the manifolds on, lubed them with silicone grease and went to install the carbs.
As you might expect I'm have problems installing the carbs. Trying to do it by myself is proving to be quite a task, I get one side started and the other pops out.
Is there a way that I can easily install the carbs? I'm sure there are "tricks of the trade" that makes this easier. My Haynes manual says nothing about re-installing the and there isn't anything on youtube that I can find.

 

[jetmechmarty]

I get one side started and the other pops out.

If you have the carburetors up to the intake boots, that's half the battle. To get the carburetors to seat you have to hold your tongue just right.
Hopefully, you're installing BS38 carburetors into holders designed for BS38 carburetors. Later XS650s have BS34 carburetors.

 

[Jim]

Installing the carbs can be a bitch for sure. If the boots are Chinese repops, it get much harder. Have a read here, comment 218. His were BS34's... but the story's the same for the 38's. OEM boots are much easier to install carb in. Are yours original, repops or OEM replacements?

 

[jetmechmarty]

George Fix's Store

 

[jetmechmarty]

Or this:
https://www.georgefixs.com/new-74-7...ers-intake-manifold-boots-gaskets-bs38-carbs/
Other than the price, I don't know what the difference is.

 

[bosco659]

I wipe the inside of the holders with a bit of gasoline and they pop in fairly easily. First time in was a chore.

 

[5twins]

They are a tight fit, and the cheap aftermarket replacements are sometimes too small, which makes things worse. You need to lube them to ease fitment of the carbs. Smear a little white lithium grease or some other type of rubber friendly lube on the manifold I.D.s and on the carb spigots. Rocking the carb set up and down as you push it in will help it pop in.

 

[Zonie]

Well I called in help and hopefully by the end of the day they will be on. With one of us on each side of the bike working in tandem we can solve this issue and go on to the next. Report to follow.

 

[bill932]

Use a heat gun to warm rubber

 

[5twins]

I straddle the bike like in your avatar pic, and grip the sides of it by squeezing my legs against it. This holds it so I don't push it off the centerstand as I'm pushing and working the carbs in. No helper needed because I "multi-task" (hold bike and push at the same time).

 

[Zonie]

I straddle the bike like in your avatar pic, and grip the sides of it by squeezing my legs against it. This holds it so I don't push it off the centerstand as I'm pushing and working the carbs in. No helper needed because I "multi-task" (hold bike and push at the same time).

Well I had a friend come by and between the two of us got the carbs on. Thanks to all who gave me advise.
Started it up and at first it idled well them it went up to 3500rpm. Now what?

 

[5twins]

Check for air leaks I guess? The manifold clamps need to be really tight, basically as tight as they'll go (until the two clamp halves touch). It's not always possible to get them all the way tight if the clamps are still the originals and the heads on their Phillips screws are buggered up at all. I replace them with Allens .....

Although the original is a little longer, an M5 x 16 works fine.

 

[Zonie]

Check for air leaks I guess? The manifold clamps need to be really tight, basically as tight as they'll go (until the two clamp halves touch). It's not always possible to get them all the way tight if the clamps are still the originals and the heads on their Phillips screws are buggered up at all. I replace them with Allens .....

Although the original is a little longer, an M5 x 16 works fine.

Now that is a good and inexpensive idea. My local hardware store is closed on Sundays so Monday it is. I will report back and you all know how this goes.
Again, thanks
John in Texas

 

[5twins]

Pull one of the original screws out and check it because if the clamps are replacements from MikesXS, they use a smaller screw, an M4.