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Post by JonW on Oct 26, 2014 21:53:02 GMT 1
People say the PWK28s are 'worth a few bhp' on an LC, but what about the 31k setup?
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Deleted
Deleted Member
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Post by Deleted on Oct 26, 2014 23:31:52 GMT 1
They work well on the powervalves too
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Post by JonW on Oct 26, 2014 23:37:39 GMT 1
yep, but I was wondering if one was a better upgrade over the other on the LC really. Im not looking for or expecting a bunch of bhp of anything but it would be better to use carbs that are known to work to give power on a bike rather than those that dont, since I have 2 sets of carbs and an Lc and a YPVS motor to build. AFAIK no one has said PWKs make power on a ypvs, just that they are easy to tune etc.
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Post by midlifecrisisrd on Oct 27, 2014 0:09:19 GMT 1
As I understood it they don't give any top end gain over the 26mm cars but improve the midrange and throttle response
Steve
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Post by JonW on Oct 27, 2014 2:21:13 GMT 1
Steve, So thats PWKs... on the LC or YPVS, or both?
Anyone have any idea what 31k carbs do on an LC?
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Post by midlifecrisisrd on Oct 27, 2014 9:06:32 GMT 1
That's pwk on ypvs and strangely jetting is totally different between lc and ypvs.
Lc seems to need larger pilot and smaller main where ypvs is smaller pilot larger main.
In my opinion the 31k lc2 carb is good. Have seen bikes make 70hp with the airbox
It's the same size just different internals
Steve
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Post by muttsnuts on Oct 27, 2014 11:50:09 GMT 1
an alternative is to get some RD250E/F or RD400 (1A3, 2R9) carbs as they are 28mm and a popular upgrade in the past, fit straight on and give good mid range gains while keeping the top end, 31k and 1UA carbs are also good, but it all comes down to what you can afford and what is available, as stated already, you can see 60 to 70bhp out of the 26mm carbs, you won't get much more though due to the restriction on air flow, 28mm cabs should be good for around 80 to 90bhp, maybe more, not had a bike do that much power yet and hit a carb flow issue !  |
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Post by JonW on Oct 27, 2014 12:11:16 GMT 1
Cheers Steve, info v much appreciated.
Mutts, thanks also. Id love to see those numbers on my bikes but Im doubting it based on the specs of these motors im building...
Real reason I asked is that I have one set of PWK28s and one set of 31Ks/LC2 carbs and two motors to build, one an LC and one a YPVS. Im really trying to match up the best bang for buck for each. Both will be fairly conservative motors (for me), the 66mm LC will probably have 'standardish' pipes (gutted 250s as i have them and I want a standard looking bike) and the 64.5mm YPVS will have hydroformed gibsons that im told make top end power. I wasnt really going to fit many other hop up parts to these bikes, tho the YPVS will get a Zeel and a Dynatek coil, the LC will be standard in the electrics dept.
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Post by jon on Oct 28, 2014 11:09:40 GMT 1
jonw, I've got 31k carbs on my standard LC engine (apart from Gibson's).
I had a set of 4L0 00 carbs with no needle jets, and thought by the time I'd got the jets I may as well have paid the extra for a set of 31k carbs that were going.
They seem to be fine (with the slightest usual flat spot) but I haven't even brought myself round to fine tune yet, as a was still running in, and I'd rather leave them slightly rich for this.
If it were me I'd definately use the 31k on the LC and PWK on the YPVS.
The logic is simple, while the 31k carbs will work perfectly well on either, the PWK is renouned to give slightly better performance on banshees and YPVSs. Therefore you may as well use this on the better performing engine, to enhance it further.
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Post by JonW on Oct 28, 2014 23:39:22 GMT 1
Thanks Jon, sounds logical mate!
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