Honda Twins banner
1 - 20 of 24 Posts

·
Registered
Joined
·
25 Posts
Discussion Starter · #1 ·
I'm going to install some threaded brass tubes into my carbs so that I can use my Morgan Carbtune to sync them. Does anyone see any reason why installing them on the yellow dot would be a problem? Any suggestions for a better location?
Thanks,
Greg
 

Attachments

·
Registered
Joined
·
6,495 Posts
I suggest you drill and install in the rubber intake manifolds.
The Hondas that have vacuum taps nearly always have them on the manifold ........

If you screw them up then, you're not out a cab, just the manifold.
 

·
Registered
Joined
·
6,495 Posts
66Sprint said:
... I'd put it in the intake "boot"......

You mean from the air cleaner to the carb??
That's awfully thin rubber there - and a great many 450/350's run Uni socks or other air cleaners (if they don't, they should be) and don't have any air cleaner rubbers anymore.
 

·
Sensei
Joined
·
27,183 Posts
Nah...Terminology difference...I meant the rubber part of the intake "boot" that holds the carb to the head....... The vacuum/atmospheric differential can only be measured accurately AFTER the carbs venturi section....
 

·
Premium Member
Joined
·
659 Posts
Make sure that you place the tubes in exactly the same spot on both sides--- I have tried it and think the exhaust preasure, hands 2 - 3 inches from the end of the muffler, is just as accurate a way to set up the carbies. Allan
 

·
Registered
Joined
·
6,495 Posts
I've done it on lots of 450's - I always thought it worked way better then doing it by feel.
Also, back in The Day, many of us ran 2-into-1 pipes, and it's almost mandantory for that...

And you have to remember that there's a metal sleeve within the front part of the rubber on 450 manifolds - so if you try to drill the hole right in the center of the manifold, you'll run into that metal part and it will goober up your hole for sure - especially if you get near the edge of the metal part, the drill bit will run off track real easy.
It also helps to freeze the manifold first- drilling a hole in soft rubber is pretty hard to do, that stuff will grab the drill bit and you could get hurt.
 

·
Registered
Joined
·
6,495 Posts
Flugtechnik said:
So where do you put them Bill? Any Pics? Any suggestions on hardware to use?
No photos, sorry - you'll figure it out.
Put it on the carb and note how far the carb sticks in, then go just beyond that.
Make them project up and out at about 45 degrees.

I always used cut-off 750 main jet holders, because we had a lot of them around, and they accepted the normal 5mm screw that caps off stock Honda manifold taps (like on the Fours, CB200/360, etc.) when not in use.

I think a lot of jet holders and stuff like that are that same thread size.
I just make sure it doesn't project into the airflow any - I always just epoxied them in.
The hole you drill doesn't have to be perfect- in fact, if it's a little smallish and irregular you actually get a better glue joint. I suppose you could even use plain ol' silicon, I wouldn't be afraid to use it.

I'm planning to make up a couple of sets soon, just haven't got to it yet, with all the travel and everything.
 

·
Registered
Joined
·
25 Posts
Discussion Starter · #11 ·
Heres where I wound up putting mine. I drilled the hole small and used epoxy. Combined with the threaded tubing it should hold (I hope). I have some small vacuum caps that fit on the brass tubes well to seal it all up when I'm done.
 

Attachments

·
Premium Member
Joined
·
1,003 Posts
:!:
 

·
Sensei
Joined
·
27,183 Posts
Yep, That would be a good location,.....I believe it is cast there for inserting an oil injection tube for two-stroke usage....
 

·
Registered
Joined
·
489 Posts
gpdesign said:
Heres where I wound up putting mine. I drilled the hole small and used epoxy. Combined with the threaded tubing it should hold (I hope). I have some small vacuum caps that fit on the brass tubes well to seal it all up when I'm done.
So that is just a tiny barb fitting with MPT on the other end? There should always be a vacuum at these ports right? I only fear that with a simple rubber cap, they may blow off if you start getting any carb popping. Guess I'll find some tight ones.

Thanks for the thread guys. I just got some new (to me) intake manifolds and will be doing this mod when they arrive. Why did Honda not do this in the first place!?!?
 

·
Registered
Joined
·
3,924 Posts
gpdesign said:
Heres where I wound up putting mine. I drilled the hole small and used epoxy. Combined with the threaded tubing it should hold (I hope). I have some small vacuum caps that fit on the brass tubes well to seal it all up when I'm done.
Where'd you get those vacuum plugs??

GB :mrgreen:
 

·
Registered
Joined
·
175 Posts
You can get them from an auto parts shop. usually a package of assorted sizes & colours. You can make more durable ones by cutting short pieces of fuel line of a size that will fit tightly over your tube and plugging one end.
 

·
Registered
Joined
·
175 Posts
I've never done it so I don't really know, but I'd try a hobby shop that deals in powered model cars/airplanes/boats. They'll have fuel fittings for model motors. Hobby enthusiasts can be very helpful and often have the skill to help you if you need it.
 
1 - 20 of 24 Posts
Top