Flat @ WOT.PWK Your thoughts, please. UPDATE

pete.v · Apr 7, 2011

I have 32 PWK kit from JS. The needle is custom. Came with #142 main and #38 pilots. Needle has 5 clip positions. I have run the gammut with all possible variables. I have a set of 150 mains that didn't really pan out. I did get a #35 and a #40 pilot and added a balance tube and have attained a great idle. The motor will respond off idle just fine and start on down the road quite nicely.

My issue now is no matter where i am in respect to RPM, WOT goes dead flat. My timing is at 30 BTDC with the Pazon unit and the plugs look neither rich nor lean being light golden brown.

The best senario is second from the top clip possition with the 142 Mains, 35 pilot left and 40 right. This is the best overall running position. However, any and all setting will suffer at WOT.

My cam is a JS stage 1 which is suppose to be like the Axtell #3 and similar to Peter Williams PW3, Megacycle 560NR.

My next thought is to start moving the timing around, possibly a degree or 2 in either direction starting on the retarded side. I am a little scared to go to the advanced side of life.

Another thought is cam timing. This cam is nothing crazy and the only real concern is valve clash which is fine. I used a degree wheel, dead stops and dial indicator to validate its position. No special instruction were apperently required yet my pressure test seems a little low but even at 120psi per side.

Hobot · Apr 7, 2011

Re: Flat @ WOT.PWK Your thoughts, please.

Just reviewing what little i know in case I run into same thing. When power picks up backing off of WOT, this implies too lean at WOT. This implies richer needle or main jet. Also might diddle float level, up a tad. 30' timing is about best compromise not to hinder top end power nor be too advanced detonation prone.
That is I doubt that if your timing seems nice every where but WOT then likely its not the main issue, even if could fine tuned better. Some times i've run into carb bowl not filling or flowing through float valve fast enough to keep up with the engine needs. Make sure tank vents ok too.

ML · Apr 7, 2011

Re: Flat @ WOT.PWK Your thoughts, please.

What sort of air filter are you running? lack of WOT indicates possibly a restriction. Try without to see if there is an improvement.
Next - do the slides actuallyt lift right up to clear the venturi? Everything else appears good so I would not mess with them at this stage.

Mick

bpatton · Apr 7, 2011

Re: Flat @ WOT.PWK Your thoughts, please.

This is probably not what's going on on your bike, but the circumstances are very similar to what went on with my bike once, so here goes. At one time I was running a 2S cam with a about 10:1 compression. It was acting like it was lean but didn't get the surge when you back off from WOT, just flat. Somebody told me it might be the coil, swapped out the stock coils for an Acell and it ran great. Something about the coils I had not being able to fire when the volumetric efficiency or effective compression ratio was actually reaching optimum when it came on the cam. Go figure.

BrianK · Apr 7, 2011

Re: Flat @ WOT.PWK Your thoughts, please.

Run at WOT for 5-6 seconds. Then back off the throttle to about 7/8 and hold it there.

Does the bike run better at 7/8 throttle than wide open?

If so, your main jet is too small.

Go up a size on the main, and repeat the test.

Best of luck.

Carbonfibre · Apr 8, 2011

Re: Flat @ WOT.PWK Your thoughts, please.

pvisseriii said:
I have 32 PWK kit from JS. The needle is custom. Came with #142 main and #38 pilots. Needle has 5 clip positions. I have run the gammut with all possible variables. I have a set of 150 mains that didn't really pan out. I did get a #35 and a #40 pilot and added a balance tube and have attained a great idle. The motor will respond off idle just fine and start on down the road quite nicely.

My issue now is no matter where i am in respect to RPM, WOT goes dead flat. My timing is at 30 BTDC with the Pazon unit and the plugs look neither rich nor lean being light golden brown.

The best senario is second from the top clip possition with the 142 Mains, 35 pilot left and 40 right. This is the best overall running position. However, any and all setting will suffer at WOT.

My cam is a JS stage 1 which is suppose to be like the Axtell #3 and similar to Peter Williams PW3, Megacycle 560NR.

My next thought is to start moving the timing around, possibly a degree or 2 in either direction starting on the retarded side. I am a little scared to go to the advanced side of life.

Another thought is cam timing. This cam is nothing crazy and the only real concern is valve clash which is fine. I used a degree wheel, dead stops and dial indicator to validate its position. No special instruction were apperently required yet my pressure test seems a little low but even at 120psi per side.

You have an OKO carb kit, and if the person that supplied it is unable to help with the correct jetting, then I would suggest finding a good rolling road dyno operator, who should be able to set up carbs and timing at the same time. Jets fitted to OKO are the same as Keihin and should be easily available.

However before rolling road set up, have you strobed the timing and made sure its advancing to the proper figure at full advance?

xbacksideslider · Apr 8, 2011

Re: Flat @ WOT.PWK Your thoughts, please.

I'm with Bob on weak ignition. Before swapping out the coils, try closing your plug gaps down to 15 thou and if that helps then go to a tight gap with an iridium center electrode plugs and then if that fixes it, start gapping up to 25 thou again. I also go to a projected nose plug when suffering from a spark quenched by combustion pressure; a projected nose locates the spark further into the storm.

And while 30* of lead helps the mid range, it might be killing the top end. Try taking it back to 28*

Oh, I should add that with the PWKs, you can actually enrichen (as opposed to choking), while riding the bike down the road, by pulling up on the enrichener; the left side is easier to get to of course.

cash · Apr 9, 2011

Re: Flat @ WOT.PWK Your thoughts, please.

And while 30* of lead helps the mid range, it might be killing the top end. Try taking it back to 28*

I'm with xbacksideslider on this one. Over the past few years four 850s I've came across that won't rev were over advanced including my own. It could be poor petrol or perhaps an 850 motor needs less advance than a 750 because of the flat top piston ? Anyhow, it costs nothing to retard the ignition.

Cash

Carbonfibre · Apr 9, 2011

Re: Flat @ WOT.PWK Your thoughts, please.

The person who is selling these de-branded OKO copies of Keihin PWK carbs, may well not have bothered to check the fuel levels, and in some cases the carbs can suffer from fuel starvation and fuel inlet drillings close to the needle valves need to be modified. Also check exactly what throttle needles are fitted, as those without any ID are as supplied by OKO and dont seem ideal for 4T applications.

More importantly though did the bike run well before the OKO carbs were fitted, and if so does it still work properly when the previous carbs are refitted?

pete.v · Apr 15, 2011

Turns out that it wasn't the carb but Cam timing and a bad Podtronics Reg/Rec(low voltage).

After taking a pressure test of the cylinder, 115 per side, I started to wonder having had 150 plus per side last fall before the updates. Made some phone calls and did some checking of the valve position at TDC looking into the exhaust port. From there you should see the exhaust valve approximately 1/8" open and the intake only slightly more. I advanced the cam 5 degrees to start and it was better and the compression(psi) went up 15 psi per side. Went back to TDC and could see that I wasn't quite there yet. Went another 5 and saw what I was looking for. The exhaust valve was about 1/8” open (on its way to close) and intake just slightly more open at TDC. Compression is back to 160 per side.

The new carbs have also proven to be great. Much smoother Idle then promised. This motor is strong with a capital S.
Bad weather here. Do not know if I will need the 150 mains yet. 142's in now. I will do a chop when I can.. 35 pilot jet in the left, 40 in the right. Needle clip second from the top as sent.

I lost my Podtronic Reg/Rec unit due to the new 200 watt stator. I thought I had a 200 Pods in it, but it was a 160 watt unit. POP! Received the unit yesterday and install it today. All well and good now.
I will try to put together a sound bite or two, this bitch is crisp.

A little spit and polish and wax on the new/used steel tank (new paint on tank and covers) and we're good for the new season.

bpatton · Apr 15, 2011

When you change the cam timing on the Commando the intake closing is the most affected. It would make sense that the compression reading would go up when you advance the cam. The intake valve is going to close sooner, nearer to BDC which would trap more air than later when the piston is further up the cylinder. It will improve bottom-end grunt but you give it back on top. It's linked to RPM only, not throttle position.

Were you able to check the float levels on the PWK's?

Carbonfibre · Apr 16, 2011

Glad have it running well now................those OKO carbs at $31 a piece are really worth looking at!

jeffdavison · Apr 16, 2011

You can't buy them individually...they have to be bought in lots of 15.

JD

Carbonfibre said:
Glad have it running well now................those OKO carbs at $31 a piece are really worth looking at!

jseng1 · Apr 16, 2011

Glad to hear that you've got it sorted out and that the bike with the new cam and carbs is running great. Looking forward to the sound bite and/or video.

Jim S

Carbonfibre · Apr 16, 2011

jeffdavison said:
You can't buy them individually...they have to be bought in lots of 15.

JD

Carbonfibre said:

Glad have it running well now................those OKO carbs at $31 a piece are really worth looking at!

Click to expand...

They can be bought individually from Ebay................a little more costly than $31, but even adding the cost of a couple of manifolds and air filters, nowhere near the $445 the US seller is charging for an OKO kit with branding removed!

jseng1 · Apr 17, 2011

When looking for te best deal on flatlside carbs - add all the extra parts necessary and do a cost anaysis. If you find some OKO carbs on ebay - Don't forget to add up the hours it takes to get all the right parts and sort everything out. Then when you get it running you'll have to make your own needles because the ones that come supplied don't work at all. Plus you'll have to find or make or re-drill the idle jets because the ones supplied don't work either. This is because its a 2 stroke carb and it will have to be re-designed to work on a 4 stroke. The manifolds will also need to be re-machined or filed by hand and have the bores smoothed with a porting tool because the quality is so terrible and rough its hard to believe - they will not even bolt on as supplied. Then you will have to convert the idle speed screw to the right side on the right side carb because they all come with only a left side idle screw - that means drilling, tapping the new location and plugging the old one. Just as important - you will have to fabricate a new right side idle mix screw with a T handle so you can adjust that side (you can't get at the original right side mix screw with a screw driver.) Add the manifold adapter rubber boots, clamps and find square O rings to fill in the gap inside the rubber boots where they attach to the carbs. Lastly you will have to make your own cables or pay Barnett $25 each for custom cables because no cables of the correct length are on the market.

By the time you are done you will realized that you would have been much better off buying a flat slide carb kit thats already set up. So take a look at ALL the FLAT SLIDE carb kits on the market that include manifolds, adapters, aircleaners, cables and everything you need including proper jetting for Nortons. Compare prices and you'll discover that the guy offering flat slide carb kits for $445 is providing the best deal you can find.

lynxnsu · Apr 17, 2011

I really do not understand why you bother to fiddle with those flatslides
a commando can outrun many moderns with its old amals
I do understand that people like to fiddle and fit some other carbs just to see what it does but if you do not know what ou are doing that leave it alone
I do like flatslides but it took me quite some time to get them sorted (keighin 39) on my Duke
However I am baffled to see people fitting them to commandos .And I honestly think they are a waste of time
They not only are out of period but also are ott (over the top) as a cmmando will run very happy on amals with are a diddle to tune
If you really want something else why not fit dell'orthos ,you can have some fun and they are period,but no you will not gain a lot
A commando is a seventies bike ,keep it like one

I fitted and fiddled with them on the Duke as they come from the same period but if I have to ask someone how to set them up then the fun is out of it and it comes down to showing off
Or do I see this wrong?

pete.v · Apr 17, 2011

lynxnsu said:
I really do not understand why you bother to fiddle with those flatslides
a commando can outrun many moderns with its old amals
I do understand that people like to fiddle and fit some other carbs just to see what it does but if you do not know what ou are doing that leave it alone
I do like flatslides but it took me quite some time to get them sorted (keighin 39) on my Duke
However I am baffled to see people fitting them to commandos .And I honestly think they are a waste of time
They not only are out of period but also are ott (over the top) as a cmmando will run very happy on amals with are a diddle to tune
If you really want something else why not fit dell'orthos ,you can have some fun and they are period,but no you will not gain a lot
A commando is a seventies bike ,keep it like one

I fitted and fiddled with them on the Duke as they come from the same period but if I have to ask someone how to set them up then the fun is out of it and it comes down to showing off
Or do I see this wrong?

Period? Really? I respect your opinion. Please respond back in 3 to 8 days.

I hope you know I'm just kidding. I couldn't help myself.

Carbonfibre · Apr 17, 2011

jseng1 said:
When looking for te best deal on flatlside carbs - add all the extra parts necessary and do a cost anaysis. If you find some OKO carbs on ebay - Don't forget to add up the hours it takes to get all the right parts and sort everything out. Then when you get it running you'll have to make your own needles because the ones that come supplied don't work at all. Plus you'll have to find or make or re-drill the idle jets because the ones supplied don't work either. This is because its a 2 stroke carb and it will have to be re-designed to work on a 4 stroke. The manifolds will also need to be re-machined or filed by hand and have the bores smoothed with a porting tool because the quality is so terrible and rough its hard to believe - they will not even bolt on as supplied. Then you will have to convert the idle speed screw to the right side on the right side carb because they all come with only a left side idle screw - that means drilling, tapping the new location and plugging the old one. Just as important - you will have to fabricate a new right side idle mix screw with a T handle so you can adjust that side (you can't get at the original right side mix screw with a screw driver.) Add the manifold adapter rubber boots, clamps and find square O rings to fill in the gap inside the rubber boots where they attach to the carbs. Lastly you will have to make your own cables or pay Barnett $25 each for custom cables because no cables of the correct length are on the market.

By the time you are done you will realized that you would have been much better off buying a flat slide carb kit thats already set up. So take a look at ALL the FLAT SLIDE carb kits on the market that include manifolds, adapters, aircleaners, cables and everything you need including proper jetting for Nortons. Compare prices and you'll discover that the guy offering flat slide carb kits for $445 is providing the best deal you can find.

Can you clarify whether or not the carbs advertised on your web site are in fact OKO? If so I wonder why there is a need to remove the OKO branding? Interesting to hear what the difference is between a 2T and 4T carb, as the carbs I have fitted to 4T bikes didnt need to be "redesigned" to work properly, and other than a bit of messing around trying different needles, set up was pretty simple.

highdesert · Apr 17, 2011

I bought a set of flat slides from Jim Schmidt here on this forum back in September.

They say PWK on them and nothing is filed off, removed, defaced, etc etc etc etc

He has stood solidly behind them in every possible regard.

They are fabulous. Much superior in stable idle and performance to my twin Amal set up.

They flow really strong, for the first time I feel my motor and carbs actually match up well.

Yes, I know there are many here who love their Amals, fine, great, happy for them.

Nobody is telling or even advising them to change from their Amals.

Jim's flat slides are not intended for those who love their Amals.

BUT, if one wants a dual carb set up that is superior in solid idle, no gas tickling, and great flow (all just my opinion), then these

well sorted out flat slides are worthy of serious consideration.

Flat @ WOT.PWK Your thoughts, please. UPDATE

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