mrriggs
XS650 Junkie
Keihin only makes one size needle jet for these little PUKEs.
Punkskalar and Travis, thanks for the leads on stiffer springs.
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Keihin flatslide PWK carburetor, oppinions, issues?
- Thread starter mrriggs
- Start date
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- Tags
- carburetors
Keihin only makes one size needle jet for these little PUKEs.
Punkskalar and Travis, thanks for the leads on stiffer springs.
One NJ for 2-stroke and 4-stroke applications? Wow, that's custom design alright! Mrriggs, I feel your pain.
mrriggs
XS650 Junkie
Well, even after getting them "dialed in", I still found myself messing with the air screws almost daily to keep it running right. The sticky slide issue has also crept back, so I figured one slide was sticking when I would let off a bit and de-synchronize the carbs. Running around with two vacuum gauges mounted to the bars confirmed this.
The first thing I did was remove and inspect the slides. On both of them, the chrome is already starting to bubble and flake off. More so on the right slide which is the one that was sticking. Simple test, swap slides and see if the problem follows it. It doesn't, so I'm probably not fighting a bad slide.
Since the stretched slide spring didn't last, I tried heavier springs. Imagine my surprise when the sticking throttle got WORSE. That could only mean one thing, the cables are sticking. Again, simple test, swap cables left and right and see if the problem follows it. After getting the cables off, the problem was obvious, there was no need to hook them back up for more tests. When I pulled on the cable end and twisted the throttle, it felt like a hack saw and there were several spots where it would catch.
After thoroughly examining the cables I determined that the problem was in the splitter. When moving it by hand you can feel several ridges that prevent it from sliding smoothly. I open it up and see gouge marks in the walls where the cable ends have been scraping. The plastic piston is way too small for the bore and just kind of flopping around in there. The cable ends stick out the sides of the piston and ride right on the wall of the sleeve.
So now the bike is grounded until I can find a replacement cable. Wouldn't you know it, today was the first sunny day since I got this bike on the road over a month ago.
The first thing I did was remove and inspect the slides. On both of them, the chrome is already starting to bubble and flake off. More so on the right slide which is the one that was sticking. Simple test, swap slides and see if the problem follows it. It doesn't, so I'm probably not fighting a bad slide.
Since the stretched slide spring didn't last, I tried heavier springs. Imagine my surprise when the sticking throttle got WORSE. That could only mean one thing, the cables are sticking. Again, simple test, swap cables left and right and see if the problem follows it. After getting the cables off, the problem was obvious, there was no need to hook them back up for more tests. When I pulled on the cable end and twisted the throttle, it felt like a hack saw and there were several spots where it would catch.
After thoroughly examining the cables I determined that the problem was in the splitter. When moving it by hand you can feel several ridges that prevent it from sliding smoothly. I open it up and see gouge marks in the walls where the cable ends have been scraping. The plastic piston is way too small for the bore and just kind of flopping around in there. The cable ends stick out the sides of the piston and ride right on the wall of the sleeve.
So now the bike is grounded until I can find a replacement cable. Wouldn't you know it, today was the first sunny day since I got this bike on the road over a month ago.
mrriggs,
Tip of the hat for your input!!!
Tip of the hat for your input!!!
mrriggs
XS650 Junkie
A few pics of what we are dealing with here.
What you are looking at is the bore of the throttle cable splitter housing. The one I have is very poorly machined. Judging by the number of people who have the same issues with sticking throttle and popping on deceleration, I doubt mine is the only one.
Sudco sells a cable [$55.60] for putting VMs on an XS650, that should also work with these carbs.
I'm going to try a Motion Pro Banshee twist grip throttle kit [$64.95] since I have wanted to convert to a dirt bike throttle anyway. I'm also hoping I can find the kit locally so I don't have to pay/wait for shipping once again.
So far, after buying jets, springs, and needles I've spent $451.66 total for this carb setup. Add to that a new throttle cable and it's over $500. A VM kit from 650 Central is sounding better all the time.
What you are looking at is the bore of the throttle cable splitter housing. The one I have is very poorly machined. Judging by the number of people who have the same issues with sticking throttle and popping on deceleration, I doubt mine is the only one.
Sudco sells a cable [$55.60] for putting VMs on an XS650, that should also work with these carbs.
I'm going to try a Motion Pro Banshee twist grip throttle kit [$64.95] since I have wanted to convert to a dirt bike throttle anyway. I'm also hoping I can find the kit locally so I don't have to pay/wait for shipping once again.
So far, after buying jets, springs, and needles I've spent $451.66 total for this carb setup. Add to that a new throttle cable and it's over $500. A VM kit from 650 Central is sounding better all the time.
I hardly have any riding time on mine, because of all the snow, but I considered buying new cables as well. Now I'm sure I will. Or see if the couple of sets of VM cables I have will work.
I'll save some money since you did all the messing around with all the jetting and I'll try the JJK needles just to see the difference. So the needles, heavier springs, and a new cable and I should be good to go.
Even when I had the VMs, I had to modify the cable, buy new air filters, a bunch of jets, and I bought lighter springs too. So basically the same "extra" parts as with the PWKs. That's just how it goes with putting these custom carbs on these bikes.
I'll save some money since you did all the messing around with all the jetting and I'll try the JJK needles just to see the difference. So the needles, heavier springs, and a new cable and I should be good to go.
Even when I had the VMs, I had to modify the cable, buy new air filters, a bunch of jets, and I bought lighter springs too. So basically the same "extra" parts as with the PWKs. That's just how it goes with putting these custom carbs on these bikes.
Punkskalar
Hugh's HandBuilt
Mr Riggs,
Is that housing alloy of some sort? Send it to me and I'll machine it nice and clean for you so there aren't any snags. No Charge buddy.
Is that housing alloy of some sort? Send it to me and I'll machine it nice and clean for you so there aren't any snags. No Charge buddy.
mrriggs
XS650 Junkie
The housing is steel. I could smooth it out but that will only make the poorly fitting coupler inside even looser and doesn't address the biggest design flaw which is having the cable ends scraping the wall. Also, I have already pulled the cable housings out of it and there is no way to put them back in because of the way it is swedged. This thing is junk and not worth the time.
Thank you for the offer.
Thank you for the offer.
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mrriggs
XS650 Junkie
Since the needles cost about as much as shipping, I'd suggest getting the JJK and JJM just so you have more options.
With a new cable you may not even need the heavier springs. I think I was just fighting that cable splitter all along and not sticky slides.
Thanks. I'll take a look at my splitter or just swap the cable before I mess with heavier springs. More money potentially saved.
mikethedruid
XS650 Enthusiast
I have owned several 4 strokes with direct acting slide carbs. My Indian has an old L&L like that. None of the ones I have owned have had push-pull throttles; they all had single cables, but stiff enough return springs so sticking is not a problem.
You can't rig a push-pull setup with cables running into the slides in any case, Mike. It's only possible with a shaft-and-bellcrank system, and only called for on very late high-velocity flat-slide designs (Mikuni RS, TM 4-stroke pumper, and HSR, Keihin CRF, and similar), some late vacuum carb designs, and EFI throttle bodies. But right, PWK's on an XS650 shouldn't require it in any case.
mrriggs
XS650 Junkie
The local bike shop didn't have the Banshee throttle kit in stock but it only took a couple of days for it to come in. I got the Motion Pro "Turbo" throttle kit #01-0345, $70.28 after tax. The "Turbo" has a little faster pull than the stock throttle, but still very streetable. The cable that came in the kit is much nicer than the Mike's cable. It's definitely not up to OEM standards but still seems to be a decent piece, works smoothly. The tag on it says "Universal Throttle" which should have been my first clue that it wasn't going to just bolt on in a few minutes.
The kit is listed as compatible with PWK 28 carbs and even came with the necessary adjusters to replace the angled adjusters on the Mike's cables. Unfortunately, when the cables were installed in the carbs, they were too short and held the slides open. To get some free play in the cables I had to file down the tops of the carburetor caps. This pic shows the left one filed down, right one to demonstrate how tall they were to start with.
The cables routed easily to the carbs. The housings and adjusters are more solid than the MIke's cables. They even have little rubber boots that slip down over the adjusters (not slipped down yet in the picture).
I ran the cable under the backbone, between the motor mounts, and straight out the front of the frame.
The cable is short so you need to have low and/or narrow bars for it to reach the twist grip.
I mounted the throttle and hooked up the cable. Wouldn't you know it, the "Universal" cable was too short for the "Turbo" throttle. With the adjuster screwed all the way in it was holding the slides open. I had to file down the throttle housing where the adjuster screws in, just like I did on the carbs, to get some free play at the grip.
With all that fun behind me, I hooked up the mercury sticks and synced the carbs at idle using the slide screws, then held it off idle and synced it using the cable adjusters. It seems to hold a sync throughout the throttle range. That is one thing I could never achieve with the Mike's cable. You could sync it right off idle but when you would open the throttle a little further it would be off by five to ten inches. Open it a little more and it would swing completely and be off by five to ten inches the other way. I was pulling my hair out trying to fine tune these carbs and it turns out it was the cables I was fighting.
I finished it right before dinner so I could only go on a short test ride. It is already running better than it ever has. I need to get some more miles on it before I'll know for sure how well it's going to work out.
The kit is listed as compatible with PWK 28 carbs and even came with the necessary adjusters to replace the angled adjusters on the Mike's cables. Unfortunately, when the cables were installed in the carbs, they were too short and held the slides open. To get some free play in the cables I had to file down the tops of the carburetor caps. This pic shows the left one filed down, right one to demonstrate how tall they were to start with.
The cables routed easily to the carbs. The housings and adjusters are more solid than the MIke's cables. They even have little rubber boots that slip down over the adjusters (not slipped down yet in the picture).
I ran the cable under the backbone, between the motor mounts, and straight out the front of the frame.
The cable is short so you need to have low and/or narrow bars for it to reach the twist grip.
I mounted the throttle and hooked up the cable. Wouldn't you know it, the "Universal" cable was too short for the "Turbo" throttle. With the adjuster screwed all the way in it was holding the slides open. I had to file down the throttle housing where the adjuster screws in, just like I did on the carbs, to get some free play at the grip.
With all that fun behind me, I hooked up the mercury sticks and synced the carbs at idle using the slide screws, then held it off idle and synced it using the cable adjusters. It seems to hold a sync throughout the throttle range. That is one thing I could never achieve with the Mike's cable. You could sync it right off idle but when you would open the throttle a little further it would be off by five to ten inches. Open it a little more and it would swing completely and be off by five to ten inches the other way. I was pulling my hair out trying to fine tune these carbs and it turns out it was the cables I was fighting.
I finished it right before dinner so I could only go on a short test ride. It is already running better than it ever has. I need to get some more miles on it before I'll know for sure how well it's going to work out.
suiteo
XS650 Enthusiast
I've been following this thread eagerly, as I too have had the sticking cable problem and some jetting issues. Thank you mrriggs for the time and effort spent working on this issue and posting it here. I STILL can't seem to dial my carbs in and get my bike running right, so I may try the needle/jetting suggestions you've worked so diligently on.
On a side note, has anyone yet found a source for a "plug and play" solution other than ordering a custom 2 into 1 cable, that won't require all of the modifications mrriggs has had to do to get these carbs to work?
Thanks,
J
Edit: Seems to me that Mike's cable could stand to be a couple inches longer. I wonder if taking these measurements into account a custom cable/group buy might be able to be set up to help members here that are having this issue? Just a thought....
On a side note, has anyone yet found a source for a "plug and play" solution other than ordering a custom 2 into 1 cable, that won't require all of the modifications mrriggs has had to do to get these carbs to work?
Thanks,
J
Edit: Seems to me that Mike's cable could stand to be a couple inches longer. I wonder if taking these measurements into account a custom cable/group buy might be able to be set up to help members here that are having this issue? Just a thought....
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mrriggs
XS650 Junkie
Try calling Sudco, Tech: 323-728-5407, Order:800-998-3529
They have a cable (#021-960) for installing VM34s on an XS650. I assume it will also work with the PWK28 carbs. Their tech guys could probably tell you for sure. This would be my first choice if I was going to keep the stock throttle.
You will also need the adjusters for the tops of the carbs. The Sudco part numbers are #018-005 for the adjuster, #018-008 for the nut.
mrriggs
XS650 Junkie
The new cable cured the carb sync issues but the slides (especially the right one) were still sticking when I let off. This time, the stiffer springs actually helped it but didn't eliminate it completely. I pulled the slides last night and inspected them. The round side looks like it was machined and is fairly smooth. All the other sides are "as cast" and had several burs, nicks, and high spots. I ran a file over them to take down the high spots. So far, even with the stock springs, the slides are returning properly.
Mrriggs, after all of your work here, would you run another set of these carbs? or would you just go down the VM path next time.?
I am/was looking at getting a set of the mikes carbs, I think you may have changed my mind.
Cheers.
I am/was looking at getting a set of the mikes carbs, I think you may have changed my mind.
Cheers.
mrriggs
XS650 Junkie
If Mike's sold the carbs outside of the kit then I would probably buy them again. I didn't run the air filters (prefer Uni filters), replaced the cables, and now I need to replace the boots (starting to split).
The carbs themselves haven't been bad, other than the sticky slides which is now remedied. The jetting issues just come with bolting non-stock carbs onto a non-stock engine. All-in-all they are pretty easy to work on and tune.
If you want to save some coin then buy Chinese clones straight from China. I've seen them for as little as $15 a pop complete with the Keihin name cast in the side. Then buy yourself a handful of genuine Keihin brass and go to town.
The carbs themselves haven't been bad, other than the sticky slides which is now remedied. The jetting issues just come with bolting non-stock carbs onto a non-stock engine. All-in-all they are pretty easy to work on and tune.
If you want to save some coin then buy Chinese clones straight from China. I've seen them for as little as $15 a pop complete with the Keihin name cast in the side. Then buy yourself a handful of genuine Keihin brass and go to town.
mrriggs
XS650 Junkie
The Sudco VM34 kit is $600, which is only slightly more than I have into these PWKs at this point.
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