Graham's 1974 Sprint V

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Re: Graham's 1974 Sprint V

Postby Tuna Cowboy » Sun Dec 29, 2013 1:49 pm

Graham's just a fiend for spending money on gas tanks.
Cheers,
Geoff
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Re: Graham's 1974 Sprint V

Postby Grahamcracker » Mon Dec 30, 2013 1:49 pm

I messed around with my pwk carb a little bit more and got it to operate a fair amount smoother at idle. I think the issue is that it isn't filling up the float bowl at idle or my throttle spring isn't strong enough to return the slide down causing "idle hunting".

It has worked good when going around town but it doesn't have my full confidence as of yet. Tempted to put my tried and trued phbh 30 on. I also dislike the vertical fuel inlet on the carb, it makes the routing for the fuel hose awkward, I had to bend some copper tubing from a fuel tap breather and put that in the hose to stop it from kinking at the inlet.
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Re: Graham's 1974 Sprint V

Postby spiderwebb » Mon Dec 30, 2013 4:09 pm

Grahamcracker wrote:I think the issue is that it isn't filling up the float bowl at idle or my throttle spring isn't strong enough to return the slide down causing "idle hunting".

no way it is a fuel flow issue due to float bowl not filling @ idle
that would never happen

you have a jetting issue that your over thinking as a dry float bowl. A float bowl never goes low unless
- the tap can't flow fast enough for the engines needs
- the float bowl rubber needle tip is sticking
- the fuel flow is being blocked @ the input to the float bowl

all the above would show up while in the mid to upped revs and while parked fuel would get past the float needle and flood top end

did you change up the idle jet to a richer / leaner setting and C how that changed up things

like gearless told me / you last week
- if the idle jet is too large that forces the tuner to set the slide height a bit too high… this intern almost allows the needle to come into the mixture @ idle.
- If the idle is too small = the slide height then is set too low which in turn is starving the top end of mixture and a lean / hunting situation occurs

my small frame carb has a 90 deg elbow on it to keep the cable from getting kinked

good luck
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Re: Graham's 1974 Sprint V

Postby Grahamcracker » Mon Dec 30, 2013 8:04 pm

Did all the recommended mods to the carb body, nothing crazy but involved getting a tamper proof torx bit set. wonder how long until i use that again haha
jetting:

Main 138
idle 50
slide 3.5
needle jjk
clip middle
mix. 1 turn out

with uni filter.

It drives great right now, just a touch below "too rich" so i'm not pulling wheelies yet.

I haven't been changing the jetting while doing this and I know that going to a higher idle jet doesn't solve it unfortunately. Haven't had the head temps go above 290, but i've only done freeway speed for a few miles so far.
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Re: Graham's 1974 Sprint V

Postby spiderwebb » Mon Dec 30, 2013 8:24 pm

Grahamcracker wrote:jetting:

Main 138
idle 50
slide 3.5
needle jjk
clip middle
mix. 1 turn out

with uni filter.

this is the small frame PWK BGM 24mm carb right…??
or is this the Spirnt's new carb…??

a 50 idle seems way too rich but that is up to you to figure out
is the mixture screw a air or fuel limiter (depends on carb type)…??

what were the mods…??
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Re: Graham's 1974 Sprint V

Postby Grahamcracker » Mon Dec 30, 2013 9:06 pm

This is the malossi bike. I think I may have found some possible hang ups on the float tonight, i'll post pics tomorrow.

The mod was some stuff to the float bowl to allow the bowls to drop lower and the drilling out a tiny hole in the carb body, the one that delivers fuel into the manifold. The idle does seem large to me as well, but runs well except for the idle hunting.
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Re: Graham's 1974 Sprint V

Postby spiderwebb » Tue Dec 31, 2013 11:16 am

my malossi had its squish way off out of the box too
it was 3+mm
hope you check this spec…!!

after getting my barrel milled it is now 1.8mm
Image
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Re: Graham's 1974 Sprint V

Postby spiderwebb » Tue Dec 31, 2013 4:06 pm

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Re: Graham's 1974 Sprint V

Postby jeffreyned » Wed Jan 01, 2014 5:58 pm

I keep looking for a "like" button. Nice work Graham!
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Re: Graham's 1974 Sprint V

Postby Grahamcracker » Fri Jan 03, 2014 10:44 am

So the modifications to the carb body made a positive impact and noticeable effect on the low end. I believe I also found some spots that float may have been getting snagged on when at an angle.
I had to take apart the carb body, tamper proof torx heads bits were required.
Image
Untitled by trumpetplayer189, on Flickr
I shaved off the tabs allowing the float bowl to sit slightly lower.
<iframe src="https://www.flickr.com/photos/31528751@N08/11675022915/player/9dcbd5635b" height="374" width="500" frameborder="0" allowfullscreen webkitallowfullscreen mozallowfullscreen oallowfullscreen msallowfullscreen></iframe>
I then snipped the tab on the float bowl off
Image
Untitled by trumpetplayer189, on Flickr
Got to use some of my new tools, the impact driver is super handy and it is rated at 135 ft lbs of torque
Image
Untitled by trumpetplayer189, on Flickr

Lastly I ground off some material that the float was scraping and possibly hanging up on
Image
Untitled by trumpetplayer189, on Flickr
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Re: Graham's 1974 Sprint V

Postby Grahamcracker » Fri Jan 03, 2014 10:51 am

Unfortunately the idle still randomly hangs up or jumps up a touch. Just put in a new throttle cable outer/inner that is the perfect length but still no dice... I'm going to recheck the squish just in case since a different crank did just go in. Maybe a fresh flyside seal is in order as well.

I'm also going to dial in the phbh carb this weekend and see if it still has the same issue. This should give me the answer if it is a fuel delivery/carb issue or something else entirely. It will also be handy to have a the exact jetting ready in case the is sudden need to swap carbs.
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Re: Graham's 1974 Sprint V

Postby spiderwebb » Fri Jan 03, 2014 11:38 am

what kind of angle is the carb set at….??

my small frame carb was perfectly flat like all small frame setups I have seen
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Re: Graham's 1974 Sprint V

Postby Grahamcracker » Fri Jan 03, 2014 12:15 pm

Last night I cut the radiator hose manifold piece at an angle so I can tilt the carb down slightly more making it perfectly level, so that shouldn't be an issue.

I dislike the routing of the fuel hose though, the inlet points straight up so I always have some bubble in my fuel line. I have the fuel hose routed through the air bellows hole and it is slightly lower than the highest point of the fuel line (highest point is the sharp angle that must be made to mount to the vertical fuel inlet (see picture below)) and this stops the bubble from going up into the tank but instead they remain in the fuel line causing a frothy fuel possible. After just going out and taking this photo I think that the air pocket in the line may be my issue. It usually isn't that bad but i'm lowish on gas

Image
Untitled by trumpetplayer189, on Flickr



That is the main reason I am going to set the phbh up, the fuel inlet can be twisted around for the optimal fuel hose routing.

I dropped my idle jet to 45 from a 50 and it is still a bit rich but feels good. I will probably drop a 40 in today.
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Re: Graham's 1974 Sprint V

Postby spiderwebb » Fri Jan 03, 2014 12:38 pm

air bellows = large frame
ok
so this is the Sprint

makes sense now
all along i bought this was about the small frame
:oops: :oops:

you could drill a hole above the air bellows hole so that the fuel line drops continually strait to the carb fuel IN pipe from the tank tap but that means drilling a hole in the frame.

nice work pal

ww
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Re: Graham's 1974 Sprint V

Postby Grahamcracker » Sat Jan 04, 2014 2:53 pm

pwk is off and phbh is on. Solved the issues it seems. I think the pwk needs a fuel pump for my setup.
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