Acceleration stutter. Full throttle denial. Ghetto rigged carbs.

[jasidok]

I’ve had this bike for a minute now. I inherited it after a dude got it running for the first time since ‘91. I cleaned the carbs. First time I’d ever done that, figured out what jets were. It kept leaking gas everywhere. The floats were all messed up. I said screw it. I bought the keihin carbs. They’re individuals but they’re awesome. I didn’t know you needed to buy anything with it though. So I altered the carb holders and the air filters (I know I need new and better air filters for sure). And got it started. Then I put in the pma from mikes with the e advancer. I checked the timing afterwards and it was on point. I don’t know how I got so lucky but literally it was good. So the headlight doesn’t work unless I touch the yellow wire to the safety relay to the battery only after the bike had started. If it’s touching before I turn the key, then it won’t start. And now it runs and sounds nice, but I can’t pull the throttle too much or it won’t accelerate. It’ll make this weird thumping / stuttering noise and lose all power. Kind of slow down too. Really weird right?? I don’t understand. Maybe the air filters are just cutting off the air to it once I pull the throttle too much? Should I try to sync the carbs even though it runs well? Except for the whole not accelerating thing..... I don’t know how to sync the carbs. I could YouTube it. But yea. I promise I scoured the web for all my answers before actually giving in and posting something.

Also.... my bike is a later ‘78 xs650e. It’s a gangster.

 

[peanut]

Apologies I wrongly assumed that you had fitted the CV type Keihin carbs (ie EZ500 /GPZ500 )that do have diaphragms so my post wasn't very helpful was it !

it would have been helpful if you listed the model type of your carburettors and linked to other posts and threads that you have made so that those trying to help you can give pertinent advice

if you have hesitant throttle response off idle and there are no electrical or ignition faults or inlet air leaks then you should be looking at your ...pilot jets , slides and idle mixture screw settings as these are the components that govern throttle response off of idle

 

[Ceed Klumper]

That's funny, I used to have Triumph Spitfires with twin SU carburettors, and I used the 'piece of hose' method to sync the carbs, which always seemed to work well. I am waiting to pick up my first ever XS650, a 1976 with the original carbs, so will see how I get on with that method.

 

[peanut]

That's funny, I used to have Triumph Spitfires with twin SU carburettors, and I used the 'piece of hose' method to sync the carbs, which always seemed to work well. I am waiting to pick up my first ever XS650, a 1976 with the original carbs, so will see how I get on with that method.

its old skool and its worked fine for over 100 years but some will scorn the idea .I used the method on countless MGB's

i had an early Spitfire ...great little car.I used to knock the rear light lens off with my leg every time I went round the back.
I remember it had no passenger floor which was a little scary for the occasional passenger and I lifted the engine out with a rope looped around my neck which is probably why I've now got DDD in my old age lol

Stick a picture up when you get your bike

Apologies jasidok for the thread hijack

 

[hogtyed]

Are the Keihins new? What's the setup on them (main and slow jet size, needle size, needle clip position)? What do your plugs looks like? Sooty, wet, grey?

It sounds like the pilot jet is running lean, but without knowing the whole picture, it's tough to diagnose.

 

[650Skull]

I’ve had this bike for a minute now. I inherited it after a dude got it running for the first time since ‘91. I cleaned the carbs. First time I’d ever done that, figured out what jets were. It kept leaking gas everywhere. The floats were all messed up. I said screw it. I bought the keihin carbs. They’re individuals but they’re awesome. I didn’t know you needed to buy anything with it though. So I altered the carb holders and the air filters (I know I need new and better air filters for sure). And got it started. Then I put in the pma from mikes with the e advancer. I checked the timing afterwards and it was on point. I don’t know how I got so lucky but literally it was good. So the headlight doesn’t work unless I touch the yellow wire to the safety relay to the battery only after the bike had started. If it’s touching before I turn the key, then it won’t start. And now it runs and sounds nice, but I can’t pull the throttle too much or it won’t accelerate. It’ll make this weird thumping / stuttering noise and lose all power. Kind of slow down too. Really weird right?? I don’t understand. Maybe the air filters are just cutting off the air to it once I pull the throttle too much? Should I try to sync the carbs even though it runs well? Except for the whole not accelerating thing..... I don’t know how to sync the carbs. I could YouTube it. But yea. I promise I scoured the web for all my answers before actually giving in and posting something.

Also.... my bike is a later ‘78 xs650e. It’s a gangster.

Having MikesXS Kein carbs will mean any information given about factory XS650 BS carbs is not applicable to your carbs..........You have been on the Kein carb thread. Those guys who posted about having their Kein carbs running well are the only ones who have posted any positive feedback on these carbs...........

 

[peanut]

Having MikesXS Kein carbs will mean any information given about factory XS650 BS carbs is not applicable to your carbs...................

why is that ?

I thought that the keihin carbs were also constant velocity carbs with slides , diaphragms , jet needles and needle jets etc and function in exactly the same way as a Mikuni CV carb or is that incorrect

How exactly is none of the advice that I posted relevant ? I'm not being confrontational .........just asking why you would post critisism of my post .......yet offer no specifics or helpful advice of your own to the poster

 

[Superjet]

Sounds as if he is giving advice on searching for Keihin threads to see what has worked for them with those carbs. It will not be the same for the stock cv carbs on the xs e.g. jetting and tuning.

 

[650Skull]

why is that ?

I thought that the keihin carbs were also constant velocity carbs with slides , diaphragms , jet needles and needle jets etc and function in exactly the same way as a Mikuni CV carb or is that incorrect

How exactly is none of the advice that I posted relevant ? I'm not being confrontational .........just asking why you would post critisism of my post .......yet offer no specifics or helpful advice of your own to the poster

All good
here is a parts diagram for KeinPWK Carbs.

 

[650Skull]

How exactly is none of the advice that I posted relevant ? I'm not being confrontational .........just asking why you would post critisism of my post .......yet offer no specifics or helpful advice of your own to the poster

Back ground. only because you have criticized my approach or the questioning of my advice..........No dramas or hassles..........just replying to your question

have been involved in another thread where the op was involved. The op was given advice from MikesXS through the site and directly answered the main question.....So my advice was specific to the OP.........

In post no 2 there was a procedure stated that it was an easy thing to do in relation to diaphragms and how to test...........The procedure wasn't explained, so that is what i call offering no specifics

 

[peanut]

Back ground. only because you have criticized my approach or the questioning of my advice..........No dramas or hassles..........just replying to your question

Thanks for the explanation........ I wanted to be clear that I hadn't posted any misinformation about bench syncing CV carbs and testing for diaphragm leaks.

Naturally I wasn't aware that the posters Keihin were of the non-diaphragm type. I wrongly assumed they would be the EZ500/GPZ500 Keihin CV carbs which do have diaphrams.

have been involved in another thread where the op was involved. The op was given advice from MikesXS through the site and directly answered the main question.....So my advice was specific to the OP.........

Ah ! ok....obviously .I wasn't aware of that . Multiple posting does make things a little confusing for sure.
Wouldn't it have been a more natural thing to do .....to simply draw my attention to the other thread and advise me of the type of Keihin carbs the poster had fitted rather than rubbish other members contributions ??

In post no 2 there was a procedure stated that it was an easy thing to do in relation to diaphragms and how to test...........The procedure wasn't explained, so that is what i call offering no specifics

The explanation was in the first few seconds of the video I posted........... but I guess I should have mentioned that in the post . I suppose I assumed that the PO would view the video

 

[peanut]

following 650skulls post I have amended my initial post .


Jazidok It would have been helpful if you listed the model type of your carburettors and linked to other posts and threads that you have made.... so that those trying to help you can give advice that is relevant. Most of us list our bikes spec when requesting advice

If you have hesitant throttle response off idle and you have eliminated electrical or ignition faults or inlet air leaks then you should be looking at your ...pilot jets , slides and idle mixture screw settings as these are the components that govern throttle response off of idle.

 

[650Skull]

Get of the grass...........Read the OP's first post, he states he bought Kein carbs........ an assumption was made without asking, and now blaming others for a conclusion.....now it is up to others to modify their way of thinking to conform ..........

I gave advice to the OP so he wouldn't get side tracked.......It wasn't a dig at anyone........Now there is a great big mountain made out of a mole hill........

 

[peanut]

Get of the grass...........Read the OP's first post, he states he bought Kein carbs.........You made an assumption, without asking, and now blaming others for your conclusion.....now you want others to modify to your way of thinking to solve your problem..........

i think you need some help with that temper of yours ...either that or put some more water with your spirits

 

[jasidok]

yea there's no diaphragm in the PWK. Plus the ones that i Have are the PWK 33's I'm pretty sure, and the kit that Mikes sells on there is for the PWK 32?? They only sell the 33 in separate orders...? I don't know. Anyways, So I got the Keihin Carbs PWK33 just by themselves. Everything is standard as far as jetting so far. I still have the stock Carb holders, I just modified a little to hold the Keihins. I still have the vacuum stock petcocks. I have a PMA, E advance and starter dual coil kit thing. I still have a battery. I checked my cam tension and it's on point. I adjusted my valves... .006" exhaust and .004" intake. I bought new spark plugs last week, and i have them at .035".
But i actually took them out today to look at them and they are just covered in black. My baby's running real rich.... so she actually won't start now either... Let me know if I'm missing anything.

Main Jet - 165
Pilot slow jet - 38
Jet needle - clip #1
idle screw all the way in.
Air mixture 3 full turns.

 

[jasidok]

following 650skulls post I have amended my initial post .


Jazidok It would have been helpful if you listed the model type of your carburettors and linked to other posts and threads that you have made.... so that those trying to help you can give advice that is relevant. Most of us list our bikes spec when requesting advice

If you have hesitant throttle response off idle and you have eliminated electrical or ignition faults or inlet air leaks then you should be looking at your ...pilot jets , slides and idle mixture screw settings as these are the components that govern throttle response off of idle.

Hey Peanut! I apologize I am not used to your format on here brother! It's The PWK 33. 1978 xs650, later model. but i havent really ruled anything out at this point man. I would love to say i have. I keep going back through and re check my steps. I bought the Clymer manual so i actually had a physical copy. Ummm I mean the wires that are leftover from the transition to the E advance and ignition may have had an influence i guess? I'm honestly stumped. Timing maybe? But now it's not starting... (insert face-palm emoji)

 

[peanut]

Hey Peanut! I apologize I am not used to your format on here brother! It's The PWK 33. 1978 xs650, later model. but i havent really ruled anything out at this point man. I would love to say i have. I keep going back through and re check my steps. I bought the Clymer manual so i actually had a physical copy. Ummm I mean the wires that are leftover from the transition to the E advance and ignition may have had an influence i guess? I'm honestly stumped. Timing maybe? But now it's not starting... (insert face-palm emoji)

no worries jasidok .
it would be helpful to see a picture of your plugs but not essential.
If its black soot coated without any oil then its running over-rich on idle as you say.

Have you adjusted your idle mixture screws yet ? how many turns out are they ?
If you are running the carb as supplied by Mikes and you cannot reduce the idle mixture sufficiently with the mixture screw then you may need to change your pilot jet to a smaller jet.. It would be worth buying a selection of jets for tuning

Jets for these carbs are incredibly cheap. You can get 20 jets for $2.00 from China which is ridiculous .
https://www.ebay.co.uk/itm/20Pcs-Se...n-Jet-kit-for-PWK-Keihin-OKO-CVK/142544130061


i'm not sure how well vacuum petcocks will work with a flatslide carb like the PWK , I have no experience with either the PWK or vacuum petcocks. If your idle speed is set on the high side the engine may draw more fuel than needed . personally I would change the petcocks for non-vacuum type . I believe you can modify the existing but I'm not sure

I don't know a lot about these carbs but recently I was thinking of buying one for my Lambretta Li200cc apparently they are the mutts nuts.
Some of these PWK carbs come with power jets to improve throttle pickup off idle not sure if yours have that. ?

 

[jasidok]

No I don't think mine does. But I am on my way to go get some jet right now. I acutally found someone in denver that has a bunch of them. So, I'm going to get a bunch of main jets and pilot jets. I absolutely need to switch to non vacuum petcocks. It's difficult, but it runs fine as long as i have it in Prime setting. only a coupe times did it stall out due to lack of gas. Overall, I freaking love these carbs. I think thewy're way different and definetely have a learning curve. But i've learned so much. They sound so great with my weird exhaust system.

Yea just super sooty on the spark plugs. I don't get why all of a sudden though it just decided not to start. It's very strange. It was at least rideable over the past few weeks. It was very rich and sometimes i couldn't push it past 60, but it worked out. and then this morning all of a sudden it won't turn on..... I'll take some pics here in a sec.

 

[peanut]

I would concentrate first on the Pilot jets and the mixture settings to get the idle mixture correct.

The idle mixture has an influence on all other throttle positions right up to 3/4 + and is really important for deceleration too.
I would try going down to 35 on the Pilot jets and resetting your mixture screws . You may find the mixture screw settings different for each cylinder thats perfectly normal.
Remember to reduce your idle tick over speed as low as possible so that you are just adjusting the Idle mixture .

You will need to sync your carbs if you haven't already done so or you'll never get it running right. I have no idea what the base line setting is for the slides but you could use a small twist drill under the slides to set the gaps equal then adjust the idle speed screws to adjust idle speed when the engine is running.

I'm assuming that you do not have the throttles linked but are using twin throttle cables yes ? in which case it could be a frustrating and time consuming job .
Do the carbs have manual or cable chokes ? make certain that both of the chokes are seating properly and not allowing some extra fuel through to make the mixture over-rich

A picture of your carb set up would help us a lot

 

[jasidok]

Wait is there a way to connect the two of them?