How to soften rubber?

Vase is a petroleum product and is never recommended for rubber ...

Yeah, I know. A little's not going to hurt it, especially if it's gone hard already. It's an oldtimer's trick - it actually can increase the life of components some would consider unservicable.

Besides, it's an inlet manifold - it's going to get plenty of petroleum products on it anyway!

.......Besides, it's an inlet manifold - it's going to get plenty of petroleum products on it anyway!

you think ???

Vase actually will deteriorate rubber and rubber based products, that is just the way it is

Silicon rubber grease is the go, how can I say this LOUDLY enough! I have been doing hydraulics all my life and it has always been the standard product, when I was an apprentice it was drummed into us to never use Vase, better to use oil if you are stuck. (acetone well, dunno if that is a good idea at all)

On the inlet Rusty a bit of filter oil is all you will get if anything at all

Well, I've tried every trick in the book, short of leaving it in acetone over night so it turns into a soggy mess, and I'm convinced that the sucker just will not go on.

So, here's my next trick.

How about if I get a piece of rubber hose and place over the outlet on the carby and the rubber inlet on the manifold? (The pink bit). And then clamp it on with two of those circle clamp thingo's that tighten when you turn the screw?

I reckon this'll work, the real question is, how will the extra length effect tuning???

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Last edited by aardvark on Sun Mar 26, 2006 12:54 am, edited 2 times in total.

I reckon this'll work, the real question is, how will the extra length effect tuning???

fuck knows.

after u've done it let us know

Well, I've tried every trick in the book, short of leaving it in acetone over night so it turns into a soggy mess, and I'm convinced that the sucker just will not go on.

So, here's my next trick.

How about if I get a piece of rubber hose and place over the outlet on the carby and the rubber inlet on the manifold? (The pink bit). And then clamp it on with two of those circle clamp thingo's that tighten when you turn the screw?

I reckon this'll work, the real question is, how will the extra length effect tuning???

the pink bit ??? are you serious ???

Back to the problem - what you are suggesting is a real *dodgy* fix mate, you will get a decent seal with the oversized bit of hose on the carby because the 'circle clamp thingo that tightens' (its called a hose clamp), will have something solid to tighten against (the carbie body) , but on the other end, it will be trying to tighten up on a rubber inlet manifold , which just won't work properly......it is a *guaranteed* source of air leaks.......

when you lengthen an inlet manifold, you increase the 'torque' , all else being equal, but suffer a decreased throttle response. If you shorten an inlet manifold, you increase the throttle response, and may even lift the HP a bit, but you will lose torque.......this is a very *basic* piece of advice only.

Get a bigger inlet manifold !! Your problems will be *much* reduced....

in all seriousness, you've lost the "lip" that goes over the carby. in the first pic theres that extra flap of rubber thats on the top of the rubber manifold, that should go around the lip on the carby.

My suggestion would be to try and cut off the remainder of that "lip" without hacking too much away, then get rubber to suit and cut a length about 3cm long. Then sand the rubber manifold to rough it up a bit, and using the right rubber glue (that will hold and ISN'T petrol solvable) glue it in place with about 10-15mm of the rubber exposed to go around the lip on the carby.

Good luck, it'll be a bit of a pain in the arse, also remember theres no such thing as too much glue, you dont want air leaks on a manifold!

What about if I place an aluminium sleeve inside the rubber?

That way the "hose clamp" will have something to tighten against?

Gos, I didn't want to buy another manifold, because the bolt holes in this one line up perfectly with the holes on the motor.

There are only 5 tools in the shed for this job.

1. beer
2. WD40
3. Hammer (has to be used on every job regardless)

and the last two go together, brute force and ignorance

EDIT* I think Gos has the mark on this one - it's not the pipe designed to fit that manifold. Assuming it's to an airfilter box, and by the look of it a single carb jobbie, $30 should buy you a pod filter that bolts onto the back of the carb

EDIT* I think Gos has the mark on this one - it's not the pipe designed to fit that manifold. Assuming it's to an airfilter box, and by the look of it a single carb jobbie, $30 should buy you a pod filter that bolts onto the back of the carb

The manifold and carby aren't designed to go together. But that's not the point. The manifold joins the carby to the inlet port on the motor. The airfilter goes on the other side of the carby, but the bike wont be running one.

What about if I place an aluminium sleeve inside the rubber?

That way the "hose clamp" will have something to tighten against?

Gos, I didn't want to buy another manifold, because the bolt holes in this one line up perfectly with the holes on the motor.

well, you could try a piece of aluminium sleeve.......it might just work.....I would still be concerned about air leaks

When I have modified reed blocks to suit other motors, you have the option of re-drilling completely (eg using TZ350 or DT400 reed blocks on an RD350LC motor), or 'slotting' the mounting holes......I know its a bit of butchery, but its better than piston seizure.......and if its on a race bike, its the last thing you need at speed.......

there is *one* other possible option - you might be able to get the carby inlet stub machined down 2mm in diameter (ie 1mm all the way around.....), this just *might* give you enough room to slide the carbie inlet into the reed-valve manifold with some rubber grease......those inlet stubs are *generally* about 3mm thick, so you won't be taking too much off, but I wouldn't recommend this if the inlet stub is already a bit thin....

bloody race bikes are a pain in the coight eh ??

Good luck mate, I have *shitloads* of reed-valve manifolds, if you get stuck let me know what the bolt-pattern is, how big your current carbie inlet is (OD), and I will have a dig around and see if I can find something that might work......

Cheers Gos,

I actually got this bit of advice from one of the seasoned bucket racers:

"You need to throw the carb in the lathe and turn the "eccentric " front of the carb concentric, and a little bit smaller diameter. If you turn it concentric to the bore just enough to "clean up" on the top of the diameter that should be enough, you will also have to machine the locating groove back in aswell. It is a bit dicey holding the carb in a Four Jaw chuck but if done carefully it shoulld be OK. It is much better to make up an expanding mandril to go in the bore of the carb, this way it is held more securely and can be held in a three jaw chuck thus allowing you to turn it concentric easily. "

I'm still trying to work out what he means...

....I'm still trying to work out what he means...

your mate from the buckets has *clearly* done this before.....

what he is talking about is how to hold the carbie (with a 'chuck', either 3-jaw or 4-jaw......basically either a 120deg 'clamp' (3-jaw) or 90deg clamp(4-jaw)...

You need to hold the carbie, so when the lathe spins up (and the carbie spins, because the 'chuck' is holding it .....*tight* !!), then you use a lathe tool to remove material from the inlet stub.....

its just like the old woodworking lathe at school, except you need to be more careful. if the chuck does not hold the carbie, then said carbie may fly across the workshop !! taking out the odd eye or forehead along the way......

The 'expanding mandrel' method is another means of holding an item....it goes on the inside of the item, then you turn the mandrel 'key', which expands the arms out and into 'solid' contact with the internal part of the item you wish to machine........in this case it is the carbie inlet.......

I wouldn't bother with re-machining the locating groove in as well , but that's just me, heh its a race bke, and the carby will be on and off a million times during the season ( and if it isn't, then you must have really good jetting skills........ )

the concentric/eccentric thing was just to confuse you, so you wouldn't try it in your own back shed !! (true story... )

I think this is the best option in your circumstances........

So Gos, are you saying I should take it to an expert?

any machine work should be done by someone who knows *exactly* what they are doing.....

all my lathe work is done by a mate........ in his shed......he has been doing this stuff for >25 years, and is pretty good at getting it right..

It will also help if the machinist is a biker, because a lot of machine shops will take 1 look at your carbie, and say the job is too difficult.....

but this method I think is about the best option you have.

Good luck mate