Topic: Making carb insulators?

[Weeburn]

So I think my carb insulators are leaking, I've checked about everything else that would cause my problem. When I rev up, the revs kind of hang, and after a few seconds settle down. It's pretty annoying. All started after taking my carbs on and off many times in a period of weeks when I was working on the bike a lot. Per the suggestions of other members here, I sprayed brake clean at my carb insulators and when I did, it bogged and stumbled/killed the engine. I've removed and inspected them, and don't see any cracks, but I want to replace them anyways.

Problem is, I haven't found any options besides paying about $100 on ebay for NOS pieces. Classic motorcycle solutions, who I got my airbox boots from (which I recommend, by the way) no longer produces them for the time being.

So me being me, I figure it's just a rubber tube. Radiator hose or some other similar rubber tubing should work if cut to fit, provided the diameters are right. I'm not concerned with fuel eating them over time, since they would be so cheap to replace if it did happen, it's not an issue.

Anyone else tried this? I don't see a reason for it not to work, the insulators are just straight, there's nothing particular about them like airbox boots.

[trueblue]

rubber tube will work, but the origional boots have a step in side them to match the internal size of the carbs and port, so you don't get a step in between.

[Ernest T]

The problem is the intake on the cylinder is a different size than the carb outlet on most models.

[TwoTired]

So me being me, I figure it's just a rubber tube. Radiator hose or some other similar rubber tubing should work if cut to fit, provided the diameters are right. I'm not concerned with fuel eating them over time, since they would be so cheap to replace if it did happen, it's not an issue.

Anyone else tried this? I don't see a reason for it not to work, the insulators are just straight, there's nothing particular about them like airbox boots.

After the apocalypse, radiator hose will be the best option, as it will allow the engine to run.  But, it is not a performance option as the I.D. is not size matched to the runner I.D., which will create turbulence and odd behavior in the higher RPMs, particularly.

You can get proper couplers from David Silver spares, if your local Honda dealer won't.

Quit #$%*in' about prices.  No one owes you parts for free or cheap, and repairing with a few correct replacement parts is still way cheaper than what a new bike costs.

[ekpent]

What bike,year model etc do you even have and have you verified that the manifolds are cracked or leaking yet. Clamps can be junk on certain bikes. ::Not much info and there are many thing to make a bike run like Crap. What kind of air filters do you have and exhaust system etc,., Radiator hose probably will not fix it.

[scottly]

If you can find straight tubing that will fit over both the carbs and the intake, it will work. Rather than radiator hose, check out some of the options available from industrial supply houses, like McMaster-Carr.
Don't worry about the step in the ID; while not ideal, it will work fine at higher RPMs.

[dave500]

i use this super duper impervious silcon hose for when i bench run engines,ive always wanted to try it on a drivable bike,if i was to id chamfer the inlet manifold slightly and take the sudden step out somewhat,ive used these hoses for ages.

and it adds to the extra cafe look that some might be chasing?

[scottly]

Yeah, that's the sort of stuff I'm thinking of Dave. Again, I won't give too much worry to the step...

[dave500]

i dont think the step will be any trouble either scottly,it might even create a "good turbulence",im an optimist though,i got that stuff from a place over the road from our work,,he knows my boss well and just gave me a foot off cut of the stuff but remarked how exspenive it is,the inside is sort of glazed and smooth and feels very tough,where as the outer is very rugged,its a lot easier to install and remove than the genuine ones.,ill go and see if i can see any numbers or other id on the stuff,i think it might be used for petrol bowsers?

[scottly]

Petrol bowsers? I don't think that was covered in the Aussie dictionary that Mick posted a while back. In any case, the hose I'm using now was called fuel pump hose or something, but it's quite a bit stiffer than the silicone hose I used to couple the turbo to the intake on my Corvair. Next time, I'll go with the silicone!

[dave500]

a petrol bowser is a commercial pump that you park next to then fill your car up with ,a petrol pump is on an engine,a petrol wowser is an econominal car.

[scottly]

OK, I'm using petrol bowser hose then!

[lucky]

I have use silicone turbo inlet hose with great success.
You can buy it in different bends and straight sections many different diameters.
It comes in colors also .

[Retro Rocket]

OK, I'm using petrol bowser hose then!

Good to see you still soaking up your Aussie education Scott....   We'll have you eating roo burgers in no time...

[dave500]

did someone say roo burgers?you have to drive over one first.

[apehanger 550]

rubber tube will work, but the origional boots have a step in side them to match the internal size of the carbs and port, so you don't get a step in between.

 So you could possibly take a smaller I.D. hose and fill that little gap where the step should be. the step is probably 3/8 inch or so. I would think that the step also would serve to keep the metal parts of the carbs and intake tubes cushioned from contacting each other.
  I had my tubes softened up nicely,but I left them in the wintegreen oil too long and they swelled in diameter--- too much of a good thing

[TwoTired]

  I had my tubes softened up nicely,but I left them in the wintegreen oil too long and they swelled in diameter--- too much of a good thing

Won't they shrink back down to size if left to air dry for a few days?

[GammaFlat]

  I had my tubes softened up nicely,but I left them in the wintegreen oil too long and they swelled in diameter--- too much of a good thing

Won't they shrink back down to size if left to air dry for a few days?

They do (first hand experience) go back to normal size. 

[andrewk]

Not sure what kind of bike you're working with, but....

New OEM insulators for a 750 can be had for about 20 bucks apiece.  That's brand new stock.

550 insulators are 9 bucks a piece, brand new stock as well.

I'm sure you could make various types of hose work, especially for the 500/550 since they are a straight shot.  750 would be a bit trickier since the insulators have some bend to them.

But for 9 bucks a piece, I'm not sure how much patience I would have messing around with various types of hose to make something that might not work as well as what's still available from Honda.

I've sounded like a broken record for Service Honda lately, but they have great prices and great service.  Great place to get OEM parts for "as cheap as you're gonna find 'em."  (http://www.servicehonda.com/)

[Weeburn]

You can get proper couplers from David Silver spares, if your local Honda dealer won't.

Quit #$%*in' about prices.  No one owes you parts for free or cheap, and repairing with a few correct replacement parts is still way cheaper than what a new bike costs.

Excuse me? First off, I never expected anyone to owe me anything. I'm a mechanic, and I've made enough fixes with things that aren't OEM parts to know when spending money on OEM parts is justified, and when it isn't, if not permanently, but for the sake of getting something to work in the meanwhile. Money's not the issue, otherwise I'd be stripping this thing down and building it from the ground up, but that's not what I want. I want to get my survivor bike running well enough, as soon as possible, to get me to work and back every day. If I wanted a new bike, I'd have bought a new bike.

And I'd rather not order from the UK and wait for customs and pay for the shipping, when I can go across the street from my work and find some hose that works well enough to be better than what I've got. Not necessarily radiator hose, but similar.

And If there's absolutely no other option, then I'm fine with buying OEM stuff and waiting for shipping, but as lucky, scottly, and dave500 posted, I generally was curious to see if it could be done with any success, and it appears that it can be. It's at least worth a try now that I see that someone else has at least attempted it with some results.


To everyone else in this thread, it's a '74 CB550K0 with a stock airbox, brand new Classic Motorcycle Solutions airbox boots, and a MAC 4-1 exhaust, with freshly rebuilt carbs, Stock size jets, all specs set to stock per the manual. Sorry I keep forgetting to mention at the beginning of the thread what I've got before asking for help


In reference to andrewk, I hadn't seen them yet that cheap. My local Honda dealers don't provide parts for bikes as old as mine

[Jerry Rxman Griffin aka MuthaF'er]

Your local Honda dealer doesn't HAVE parts for bikes as old as ours. Doesn't mean he can't get many of them. We usually go in with the part number in hand knowing whether or not Honda still supplies them. We then tell them to order them for us and they show up in 1 week.

[SOHC Digger]

You can get proper couplers from David Silver spares, if your local Honda dealer won't.

I see they only offer positions 1 & 3.  Am I correct in assuming 1 and 4 are the same and 2 and 3 are the same, just upside down?  So if I wanted to replace all four of mine I would just have to order 2 of #1 and 2 of #3?

[TwoTired]

You can get proper couplers from David Silver spares, if your local Honda dealer won't.

I see they only offer positions 1 & 3.  Am I correct in assuming 1 and 4 are the same and 2 and 3 are the same, just upside down?  So if I wanted to replace all four of mine I would just have to order 2 of #1 and 2 of #3?

I believe that is true.

[DJ_AX]

You can get proper couplers from David Silver spares, if your local Honda dealer won't.

I see they only offer positions 1 & 3.  Am I correct in assuming 1 and 4 are the same and 2 and 3 are the same, just upside down?  So if I wanted to replace all four of mine I would just have to order 2 of #1 and 2 of #3?

I believe that is true.

Yes indeed it is

[SohRon]

I keep forgetting to mention at the beginning of the thread what I've got before asking for help

Put it in your signature line and you'll never have to mention it again.

My opinion is just buy the parts you need; I mean, $9 apiece. Using a hose will effect turbulance, flow and a host of other things.

And, no,  there's no difference between the insulators for the 550, all four are exactly the same; the stacks for the airbox plenum are different, but you're talking insulators, right?

[TwoTired]

My opinion is just buy the parts you need; I mean, $9 apiece. Using a hose will effect turbulance, flow and a host of other things.

I agree.
How many people go out of their way to drive the bumpiest, most potholed, crumbling roads that they can find, routinely?
That's like putting water hose on the carbs to save some pennies. 
When the correct parts are NLA, then you do what you gotta do, and live with debilitated operation.

Cheers,

[754]

 I think a lot of the webers used straight tubing except the RC manifolds... so we have been running with the step in ithem for decades, and it works well . I suppose if we made proper ones, they would run EVEN BETTER....
 There was a guy on here last year was going to make the rubbers to order for K7 and or Automatic.. and he was going to make us some for webers.. reasonable.. cant remember the name he went by..

[apehanger 550]

  I had my tubes softened up nicely,but I left them in the wintegreen oil too long and they swelled in diameter--- too much of a good thing

Won't they shrink back down to size if left to air dry for a few days?

  Well. It has been a few days and not much sign of reduction in swelling,but they are grossly oversize. I am getting new ones,but I do have a few ideas on trying to get the old ones back---
  First,I will try the crock pot [hot water] at the low setting for a few hours to possibly drive some of the wintegreen oil out, then air dry for a few weeks and repeat if necessary. Containment in a sleeve of conduit or PVC pipe while soaking might have been a good option as well.
  It is really about sharing knowledge at this point,as mine are the $9.00 ones. The originals were so hard at the outset that they were like plastic and not rubber. If they can be made useable,it would be good to know if the boots ever become un-obtainable.
 It may be a while,but I will share the info on the old ones as it becomes known