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HS4 SU Jet Tubes

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richberman

richberman

Jedi Warrior
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Hi everyone. I have a tri-carb HS4 setup on my BN4. I started her up yesterday and she started easily and sounded pretty good. I then started smelling some raw fuel so I popped the bonnet to investigate and noticed fuel running from the bottom of the rear float bowl. Upon feeling under the bowl I touched the tube/spring and the tube literally crumbled in my fingers. I then looked a bit more and noticed leaking from the front float bowl also. Touching that tube and it also crumbled....
These carbs were 100% rebuilt about 14 years ago. I'm wondering if it's the ethanol in the fuel causing this or were the tubes defective?. Are the currently available tubes more resistant? Am I missing something? Do I need to completely remove the carbs to replace the tubes or can it be done in situ? I've never had to replace them because I had sent them to Tom's Imports the first go around. Any help is much appreciated......I'm bummed because I'm thinking I will need to re-tune the carbs after I finally got them tuned so nicely.
Cheers,
Rich
 
Degradation must be due to blended gas or E10 with 10% ethanol v/v and perhaps age. I've not heard of any reports of this type, but for obvious safety concerns, it's great that you were able to catch it. All 3 jets need replacing. Remove carbs, remove what remains of the degraded jets - also double-check that the o-ring seal at the bottom of the float bowl is removed. Your new replacement jets will require centering - not too difficult - and retuning.
 
If the tubes were replaced 14 years ago, they should be ethanol compatible. If they were not replaced, or replaced with NOS parts, they may not be. The same goes for other rubber parts.
 
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