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primer bulb and pulse line

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jaydub

Joined: 07 Jan 2020
Posts: 74

Posted: Wed Apr 05, 2023 3:24 pm Post subject: primer bulb and pulse line

In addition to the fuel line question I just posed, what primer bulb has held up well? The one I had in my CGS Hawk years ago got a crack and the fuel line was sucking in air so the engine quit in flight. I was able to squeeze the bulb to get fuel to the engine to restart and I kept squeezing until I got back to the airstrip with fuel running down my arm. Is there a quality one recommended?



Also, what pulse line size/material is recommended these days for the single carb mikuni pulse pump?



Thanks again,

Jay

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ridefst

Joined: 18 Oct 2019
Posts: 16
Location: Ohio

Posted: Thu Apr 06, 2023 3:41 am Post subject: Re: primer bulb and pulse line

I've heard various stories about those primer bulbs deteriorating internally, and sometimes blocking fuel flow completely.  I'd avoid them.

If you have an electrical system an electric pulse pump like Steve mentioned is great, or else a push/pull hand primer pump.

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stuart(at)harnerfarm.net
Guest

Posted: Thu Apr 06, 2023 5:27 am Post subject: primer bulb and pulse line

My kit came with the bulb and some tee-'s.



The bulb goes in the main fuel line and you put a tee in before and one 

after the bulb. Then run a short piece of hose between the tee's.



In this configuration you have to pinch the bypass line when using the 

primer.



The idea was that if the check valve failed and blocked flow through the 

bulb the engine could still pull through fuel through the loop.



I was told that there was at least one occurrence of an engine out 

caused by an internal failure of the bulb. Maybe more.



There wasn't any discussion of the bulb failing on the outside, but 

considering they look like off the shelf primers for boats it wouldn't 

surprise me.



The push/pull primers would certainly work but would require using tee's 

and pinching the main line while priming as they shut off the flow when 

closed and locked. I don't think you could rely on passing fuel through 

them for regular flight.



Here is a picture of how it is set up. The original hose was just plain 

clear plastic but it was getting hard after a few months so I went to 

the snowmobile shop and got some urethane hose which is not clear but 

you can still see the fuel inside. It will last a year of two before 

needing replacement.



Another option is just plain automotive black rubber fuel hose. Lasts a 

lot longer but you can't see the fuel through it.



Stuart



On 4/5/23 18:23, Jay Dub wrote:

 	  Quote: 	
		   



 In addition to the fuel line question I just posed, what primer bulb has held up well? The one I had in my CGS Hawk years ago got a crack and the fuel line was sucking in air so the engine quit in flight. I was able to squeeze the bulb to get fuel to the engine to restart and I kept squeezing until I got back to the airstrip with fuel running down my arm. Is there a quality one recommended?



 Also, what pulse line size/material is recommended these days for the single carb mikuni pulse pump?



 Thanks again,

 Jay

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jaydub

Joined: 07 Jan 2020
Posts: 74

Posted: Thu Apr 06, 2023 7:22 am Post subject: primer bulb and pulse line

Hi Again all,

I appreciate the replies. The reason I want the bulb is in case the pulse pump goes kaput in flight. Having it reachable in my CGS Hawk could have been a lifesaver as I was over a large mature woods (couldn't have landed anywhere but in >100' tall trees) but since I could pump it by hand I was able to do a restart and safely fly back to our airstrip. I'm building my plane very light and I won't have electric so an electric pump is not an option. Yes, I learned the hard way about the bulb cracking then I learned later that the fuel lines and bulb should be replaced annually. While I can be frugal, fuel lines, filter, and bulb are cheap insurance. I hadn't heard of primer bulbs getting blocked so Stuart's solution with a bypass makes sense. The bulb that came with my CGS Hawk kit in 91 wasn't a good quality bulb hence my asking if anyone knows of a good quality one. The bulb that came with the Kolb kit I purchased is for a blood pressure cuff and I don't see how I could even make that work (only has an outlet and no inlet barb) plus it's extremely low quality.  That may have come from the previous owner, not Kolb. For engine starting I'm not a fan of the push-pull primers and I will be using the Bing enriching circuit instead but to each their own on that. 



I did look through my kit materials last night after sending the email and I found I do have a bunch of "Superthane Ester 1/4" ID x 3/8" OD" tubing that must have come from Kolb. I'll probably use that to begin with as it's never had fuel in it, it's quite supple, and it's not been outside to get UV. Since it's so supple I think I should use a stiffer tubing for the pulse line.



Jay

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Ceengland

Joined: 11 Oct 2020
Posts: 381
Location: MS

Posted: Thu Apr 06, 2023 7:43 am Post subject: primer bulb and pulse line

On 4/6/2023 10:22 AM, Jay Dub wrote:

 	  Quote: 	
		   



 Hi Again all,

 I appreciate the replies. The reason I want the bulb is in case the pulse pump goes kaput in flight. Having it reachable in my CGS Hawk could have been a lifesaver as I was over a large mature woods (couldn't have landed anywhere but in >100' tall trees) but since I could pump it by hand I was able to do a restart and safely fly back to our airstrip. I'm building my plane very light and I won't have electric so an electric pump is not an option. Yes, I learned the hard way about the bulb cracking then I learned later that the fuel lines and bulb should be replaced annually. While I can be frugal, fuel lines, filter, and bulb are cheap insurance. I hadn't heard of primer bulbs getting blocked so Stuart's solution with a bypass makes sense. The bulb that came with my CGS Hawk kit in 91 wasn't a good quality bulb hence my asking if anyone knows of a good quality one. The bulb that came with the Kolb kit I purchased is for a blood pressure cuff and I don't see how I could even m!

   ake that work (only has an outlet and no inlet barb) plus it's extremely low quality.  That may have come from the previous owner, not Kolb. For engine starting I'm not a fan of the push-pull primers and I will be using the Bing enriching circuit instead but to each their own on that.



 I did look through my kit materials last night after sending the email and I found I do have a bunch of "Superthane Ester 1/4" ID x 3/8" OD" tubing that must have come from Kolb. I'll probably use that to begin with as it's never had fuel in it, it's quite supple, and it's not been outside to get UV. Since it's so supple I think I should use a stiffer tubing for the pulse line.



 Jay

I have very limited experience with Rotax 2strokes, but I did have a 
	


little. I used the blue-green urethane tubing initially when I restored 

an old Kolb Twinstar with a 503. I made a 'flop tube' with filtered, 

weighted pickup to go in the tank, using the urethane tubing. Within a 

year, the tubing rotted in two at the fitting inside the top of the 

tank. I replaced the flop tube pickup with a bottom-feed on the tank (I 

discovered that hoses that have fuel proof coverings are shockingly 

expensive). I replaced all the blue line with quality black automotive 

fuel line.



I bought a ~$10 squeeze bulb during restoration, and it, too, rotted 

within a year. Coming from the bigger/heavier experimental world, that 

unnerved me as unacceptable performance for such critical items. After 

researching the cost of quality squeeze bulbs, I elected to install a 

clone of the Facet cube pump, and a little 4AH AGM battery. I had a bulb 

primer on an outboard back in the early 1990s that was probably 20 years 

old and still worked fine, but when I priced the 'brand name' primers 

from Evinrude, Johnson, etc, they were more expensive than the 

conversion to electric primer.



One upside to electric is that you flip a switch and go back to flying, 

instead of focusing on squeezing the bulb in flight.



FWIW,



Charlie

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