Ongoing Fueling issues

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Beef
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Re: Ongoing Fueling issues

Post by Beef »

Well,
2 days at Cadwell and all isn't well!......

Bike ran lovely in the morning of saturday as I was learning the track, as my confidence grew, so did my balls!!
Braking as late as possible for Park, saw the bike bog down as bad as ever when asking for power mid corner, I couldn't get it to clear and run clean until after the mountain - which when you're a biff doesn't build confidence!!

Went and spoke with freeride Nick, he mentioned the 'ol breather mod', I said no, I'd done that! Went back to the bike, grabbed a torch and looked for piece of mind........pipes were back in the frame ala standard set up!! :confused :confused
I can only think that the dyno guy had put them back after he fitted the plastic air dam! :lol:

Out again in the afternoon and braking last safe moment sees the bike bog down buy nowhere near as bad, it would be clear by Chris Curve, so that tells me it's still flooding the front carb (you know, with all my years of experience and knowledge of VTR's :lol: ) After the session, I looked at the front overflow pipe and it was dripping, when I bent it down a tubefull of fuell cam out!

For the rest of Sat & Sunday I just throttled off approaching Park and braked earliergentler & had a sweet running bike all day!

As I've said before, I do have the CBR pump fitted & all I've done with the overflows is pull them out the frame.

Does anyone have any incling what could be going on?
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Wicky
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Re: Ongoing Fueling issues

Post by Wicky »

"I looked at the front overflow pipe and it was dripping"

Track the hose back to the source - Is it to the tank filler overflow? How much full is the tank when racing?
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Beef
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Re: Ongoing Fueling issues

Post by Beef »

Hi Wicky, it's the pipe from the front carb overflow!
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Beef
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Re: Ongoing Fueling issues

Post by Beef »

Hello all, I am at Cadwell again on 19th & 20th. Over the last few months I've been doing some digging into my ongoing fuelling problem..... I read on the FB group about the carb sponges & breather system for the diaphragms. Well I somehow managed to lose a cover at some point - I did make a Heath Robinson replacement... but I couldn't tell you how effective it was, I also noticed that the filter had perished, at the time I was at the track so I Heath Robinson'd that too :lol: :lol:

Anyway, I have purchased new filters and got some new K&N covers to seal them from airbox. Could this cure my problems?......... :think:
tony.mon
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Re: Ongoing Fueling issues

Post by tony.mon »

Were you running it with one of the triangular sealing boxes missing?
That will certainly affect it, as the carb opening is determined by the difference in pressure either side of the diaphragm.
It's not falling off, it's an upgrade opportunity.
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Beef
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Re: Ongoing Fueling issues

Post by Beef »

It was missing, but I had a gaffer tape replacement. When I took it to the dyno last year, I had trimmed the covers out of a standard filter housing...but I can't actually remember how that looked. I will be in the shed this weekend, I shall fit the new sponges and my ebay purchased K&N rubbery caps. I'll stick a pic on of my 'fix'...….
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Beef
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Re: Ongoing Fueling issues

Post by Beef »

New filters fitted with the new caps. The old ones seemed pretty well sealed but my bodge with a kitchen sponge might’ve been preventing some airflow in/out! :silent:
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Beef
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Re: Ongoing Fueling issues

Post by Beef »

A good one & a half days at Cadwell (weather washed out Wednesday afternoon)
Still issues with fuel, it has to be starvation as it only happens after the longest straight. It is also worse with less fuel in the tank than full. (When it plays up, the exhausts pop and bang like it’s about to run out of fuel)
If I braked at the 200m board it would play up When I fed the power back in. Depending on how full the tank was, this could last 1-2 bends or all the way to the mountain! If I braked at the 300m board therefore nowhere near as hard- like I was on an IAM assessment, I’d have no issues at all.
I have a fuel pump sat on the tail of the rear subframe, I’ve replaced all the fuel lines so I know none are perished/causing issues.
I Know I can go out full to the brim But at the end of the session, the problem would still arise! I assume it can’t be an issue with fuel tank breather as it clears itself, if there was a vacuum, it would eventually cut out and I’d have to remove fuel cap to allow air in?
Would moving the pump to somewhere else?
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Beef
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Re: Ongoing Fueling issues

Post by Beef »

Meant to add - could the fuel tap be an issue?
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freeridenick
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Re: Ongoing Fueling issues

Post by freeridenick »

Beef wrote: Fri Aug 21, 2020 10:41 am Meant to add - could the fuel tap be an issue?
Could be. It's worth stripping it to make sure there are no splits.

Is the fuel pump sticking? The contacts under the black cap wear and can stick at worst. At best they don't move fast enough which has a knock on effect to fuel delivery. At least as I understand it.

Mine were sticking to the point where I had to whack the pump with a hammer on a track day. Back home I checked the contacts and they were noticeably worn. Easy job to replace - YouTube is your friend - and when I turned the ignition on the clicking was much less lazy.

Maybe on WOT it's using more fuel than the pump can deliver, so it's the long straight not the braking that's the problem.
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Beef
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Re: Ongoing Fueling issues

Post by Beef »

Thanks Nick, I’ll check the pump. TBH, I don’t think WOT is the issue as I’m hitting the same sort of speeds every time, the only difference is how gently or hard I brake.
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Re: Ongoing Fueling issues

Post by tony.mon »

Beef wrote: Fri Aug 21, 2020 2:52 pm Thanks Nick, I’ll check the pump. TBH, I don’t think WOT is the issue as I’m hitting the same sort of speeds every time, the only difference is how gently or hard I brake.
Yes, but if you brake gently the float bowls have more time on a closed throttle in the braking period to recover their level.

Try removing the fuel tap internals, and sealing off the breather stub.
When I ran a fuel pump it was the tap that caused my issues.
It's not falling off, it's an upgrade opportunity.
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Beef
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Re: Ongoing Fueling issues

Post by Beef »

I’ve ordered a new set of points for the pump. So will fit them as a matter of course. I’ll take your advice and pull the tap apart.
What do you mean by sealing breather stub? (will probably be obvious when I’m there)

Tony, did you fit a manual Tap/petcock?
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freeridenick
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Re: Ongoing Fueling issues

Post by freeridenick »

Beef wrote: Fri Aug 21, 2020 7:31 pm What do you mean by sealing breather stub? (will probably be obvious when I’m there)
The one that points down, i.e. not the one the vac tube goes on.
tony.mon
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Re: Ongoing Fueling issues

Post by tony.mon »

Actually, I bypassed the diaphragm by sticking a paperclip in, to prevent the diaphragm closing...
It was a bodge, but it worked fine.

I found that the pump "vacuum" pulled the diaphragm closed.
It's not falling off, it's an upgrade opportunity.
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