Down the rabbit hole I go
- Thread starter Nduetime
- Start date
I assumed that... I'm going to pull the new plugs tomorrow to see what they look like. Prior to my oil change tonight the bike was never running for more than 1-2 minutes and the plugs were oily. I'm hoping it's just a air/fuel problem and not an indication that I need to replace piston rings. That would be something I'd like/have to put off until next winter.
Almost forgot. After my oil change, when it was running and idling high, I put my hand over the carb and restricted the air flow. In doing so, I was able to get the idle to drop way down. The engine sounded pretty good at about 1500-1800 rpm's but I managed to get it down to 1100 rpm where it really sounded like it was struggling. From my research, that would indicate a lean condition, no? As soon as I removed my hand from the carb, it surged back up to 3500-3800 rpms.
I promise, this is my last post for tonight. I'm done. Thanks again firebane!!!
I promise, this is my last post for tonight. I'm done. Thanks again firebane!!!
firebane
braaaaaaaaaaap
Its really hard to say.. Lets get more information about your setup before really making any conclusions..
Oh and here is a short video of my bike that start running after 25 years in storage with open pipes lol.. You can hear near the end how the idle starts creeping up lol!
https://www.youtube.com/watch?v=uNiIaYHx2MM
Oh and here is a short video of my bike that start running after 25 years in storage with open pipes lol.. You can hear near the end how the idle starts creeping up lol!
https://www.youtube.com/watch?v=uNiIaYHx2MM
Yes, that bike did have a crossover between the exhaust pipes. The crossover helps balance out the pressures between the two and will certainly affect how the bike runs.
firebane
braaaaaaaaaaap
Oooph that poor bike someone has really messed around with with far too much.
That carb setup looks like something that someone did over on kz400 forums and I do much agree that it needs to be built proper. That silly setup for air acting as a pretend filter needs to and a proper one installed. The fuel lines and fuel filter look old and could use replacing.
The exhaust is technicall fine but when it was change it would need to be rejetted but with a different carb well who knows.
Its not that you got yourself into a mess but that bike is a mess and if your willing to take some time and figure out stuff it shouldn't be too bad to get running nice. I would be going on ebay and looking at proper pipes for the bike either a new set or get replacements that didn't have the cross over.
The carb should be fine but you'll need to track down the make of it so you can get the proper jets and take it apart to find out what the current jets and such are in it.
Good luck
That carb setup looks like something that someone did over on kz400 forums and I do much agree that it needs to be built proper. That silly setup for air acting as a pretend filter needs to and a proper one installed. The fuel lines and fuel filter look old and could use replacing.
The exhaust is technicall fine but when it was change it would need to be rejetted but with a different carb well who knows.
Its not that you got yourself into a mess but that bike is a mess and if your willing to take some time and figure out stuff it shouldn't be too bad to get running nice. I would be going on ebay and looking at proper pipes for the bike either a new set or get replacements that didn't have the cross over.
The carb should be fine but you'll need to track down the make of it so you can get the proper jets and take it apart to find out what the current jets and such are in it.
Good luck
Alright, thank you guys for your help. Sure enough, the bike was previous owned by someone on the KZ400 forum. He had plans of making it into a bobber. The bike came with about 5 additional slow jets and one additional main jet. I'm at the point I think I'd like to explore the option of seeing what I can get out of what I have. I have have no problem switching to a different carb set up but given that the PWK 35 has been sucessfuly converted for the KZ400, I'm likely to think it can be accomplished. Again, I have no problems purchasing the parts needed. and i'm not pushing for this to be finished in a week or three. This is a project and a learning one at that. My immediate goal is to get the bikes idle down to an appropriate level. Tuning it from there would be next. I understand changes to each component will effect the jetting but that's something that doesn't take much more than removing the carb and changing the jets appropriately. A set of new main jets and slow jets are ~$40. Add a filter for ~$40 and new boots for ~$60 or a 11th hour for $150 and I'd have what I need to get the bike running better than where it is now. Hell, just a new carb would cost me what the new price for the jet sets, filter and boots would. The replacement exhaust is a given regardless of sticking with the PWK or moving to a VM. Same goes with new filter and fuel lines. This is a four stroke motorcycle, not a jet airplane, it's shouldn't be that complicated or so far from figuring out, right. I'm not looking for immediate gratification here, I can't afford that!
firebane
braaaaaaaaaaap
Nduetime said:
Then you have the right mindset to make this bike work for you. You need to start from one area and work back. I would start with the exhaust to get it cleaned up and fixed proper. Then intake, jets, air filter, and fuel filter to get the bike running better.
From there its all small stuff to make it your own.
I hate to break this to you but that will never work very well and it's not just an issue of jetting. If that abomination of an intake manifold leaks that will cause a high idle abut choking the airflow doesn't really reveal a lot. I'd get a pair of carbs and an airbox but maybe that's just me.
An alternative is an airbox and single large filter.
That doesn't mean that you can't get it to run better than it is at the moment. Take it to a shop with a dyno and get them to test it and do an exhaust gas analysis. That is the fastest way to get it close to the right air: fuel ratio.
An alternative is an airbox and single large filter.
That doesn't mean that you can't get it to run better than it is at the moment. Take it to a shop with a dyno and get them to test it and do an exhaust gas analysis. That is the fastest way to get it close to the right air: fuel ratio.
xb33bsa and teazer, I hope I wasn't coming off like I was discounting what you have to say or that I'm so stubborn in my ways that I'm not welcome to criticism. I thought that a single carb setup would work and since I've read of people having claimed success, I was thinking my ability of achieving it wouldn't be unheard of. Based solely on that, I was confused by why I was receiving such pushback on the setup.
I read a lot of forum where newcomers of some new hobby are being told/discouraged to even try what they want to achieve because it is nearly "impossible" due to their lack of knowledge/skills. For me it's always difficult to stomach said approach. I'm not saying everyones ideas are good or correct. However, just because someone lacks the experience doesn't mean that person can not accomplish what they set out to accomplish. Hell, they may discover a new talent they didn't know they possessed. Now I'm not saying this is what happened, I'm just stating that this was one of the thoughts that crossed my mind when I read how the bike can't run properly with a single carb setup. Now that I understand a bit more and given the explanation of the current manifold design, I can accept that the current manifold will not allow me to achieve my ultimate goal.
I suppose I should clarify something at this point. I want a great functioning bike. I'm not out to have the coolest looking setup. After all, form follows function! Based on my budget and experience, my goal will take some time. But I welcome it and am excited to learn every bit of the way. I certainly don't have the money to just go out a purchase everything I need at once. Given what I have, I suppose I could take an approach that will allow me to reach my ultimate goal at my own pace. Thoughts on the following? Please don't hold back in opinions. I'm a straight up guy that likes straight up answers. I throughly enjoy each response.
1. Get the bike functioning better than what it is now, knowing it's not idea or even close to what it should be, using my single carb setup. In no particular order, this would include but would not be limited to: installing a proper air filter, identify and address manifold/boots air leaks, replacing the fuel lines/filter and replacing the exhaust. Jetting "closer" to ideal than where it is now.
2. Once the above is achieved, I could then purchase an additional PWK 35 carb and eliminate the manifold all together by bolting them straight to the head. Re-jet as necessary.
I read a lot of forum where newcomers of some new hobby are being told/discouraged to even try what they want to achieve because it is nearly "impossible" due to their lack of knowledge/skills. For me it's always difficult to stomach said approach. I'm not saying everyones ideas are good or correct. However, just because someone lacks the experience doesn't mean that person can not accomplish what they set out to accomplish. Hell, they may discover a new talent they didn't know they possessed. Now I'm not saying this is what happened, I'm just stating that this was one of the thoughts that crossed my mind when I read how the bike can't run properly with a single carb setup. Now that I understand a bit more and given the explanation of the current manifold design, I can accept that the current manifold will not allow me to achieve my ultimate goal.
I suppose I should clarify something at this point. I want a great functioning bike. I'm not out to have the coolest looking setup. After all, form follows function! Based on my budget and experience, my goal will take some time. But I welcome it and am excited to learn every bit of the way. I certainly don't have the money to just go out a purchase everything I need at once. Given what I have, I suppose I could take an approach that will allow me to reach my ultimate goal at my own pace. Thoughts on the following? Please don't hold back in opinions. I'm a straight up guy that likes straight up answers. I throughly enjoy each response.
1. Get the bike functioning better than what it is now, knowing it's not idea or even close to what it should be, using my single carb setup. In no particular order, this would include but would not be limited to: installing a proper air filter, identify and address manifold/boots air leaks, replacing the fuel lines/filter and replacing the exhaust. Jetting "closer" to ideal than where it is now.
2. Once the above is achieved, I could then purchase an additional PWK 35 carb and eliminate the manifold all together by bolting them straight to the head. Re-jet as necessary.
firebane
braaaaaaaaaaap
Don't get discouraged and only take what people say with a grain of salt. Yes these people have been around and they have tried many things and know what may or may not work. But no two situations are the same and you may have different luck than others.
Don't forget your working on a bike that isn't as popular as all the other hondas other there so the information is as vast and sometimes we are the pioneers to figure out what works for others.
Don't forget your working on a bike that isn't as popular as all the other hondas other there so the information is as vast and sometimes we are the pioneers to figure out what works for others.
So, to many of you, the solution to my idling problem may be elementary. However, for someone like me who has never worked on a motorcycle or a carburetor before, I am rather please with my discovery. I'll first start by restating the problem.
At starting, the engine runs up to ~3,500 - 3,800 rpm's and stays. Blip the throttle, it raises and stays. Blip again, same result, never dropping in rpm's. Here's a video showing this:
http://s13.photobucket.com/user/nduetime/media/kz400/1.mp4.html
So yesterday I decided to tackle some other things that needed verifying/addressing. I measured the points and found them to be at ~.53mm. Adjusted them back down to ~.35mm. I then readjusted the timing (statically.) Here's a video showing those results:
http://s13.photobucket.com/user/nduetime/media/kz400/2.mp4.html
So at that point, I managed to drop the rpm's a bit but it was still very high. Turning the idle adjustment screw didn't change anything. All the way in or all the way out, no difference. I decided to stop for the evening to allow myself time to process the situation. I knew from Saturday that there's air leak/s at the manifold/boots. Given the bike races and doesn't retreat, I kept thinking it had something to do with the cable. However it has plenty of slack and isn't kinked. The more I thought about it, the more I was certain it had something to do with the slide staying open.
I spent 6-8 hours reading and watching videos on issues like I was experiencing. I found myself going back to the PWK carb diagram, which I've been studying for the past week or so. I kept thinking, what would cause the slide to stay open and not retreat? Stuck cable, improper idles adjustment screw position, faulty spring. Then it hit me...if the spring compresses and doesn't return, the slide won't return to where it needs. I knew from looking at the diagram the spring contacts a collar at the carb side. I remembered mine didn't have one when I took it apart. The collar plays a vital role. The more the throttle is engaged, the more the spring is compressed. Without that collar to keep the spring end stationary, the spring continues to jam down inside the slide, resulting in the slides inability to return to being fully seated.
After work today I decided to put my theory to the test. I cut out a "collar" (basically a couple of washers) from a plastic water jug and placed them between the spring and the cable holder and reattached the cap to the carb. Here is the result:
http://s13.photobucket.com/user/nduetime/media/kz400/3.mp4.html
With my makeshift collar in place, the spring is unable to seat down into the slide and allows the throttle spring to compress and extend properly. With a much more manageable idle, I was able to play with the idle adjustment screw. Doing so resulted in being able to adjust the idle up and down.
So, a very small discovery that is probably a given to many others was a large accomplishment to me. Super excited now. This is going to be a fun ride!
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At starting, the engine runs up to ~3,500 - 3,800 rpm's and stays. Blip the throttle, it raises and stays. Blip again, same result, never dropping in rpm's. Here's a video showing this:
http://s13.photobucket.com/user/nduetime/media/kz400/1.mp4.html
So yesterday I decided to tackle some other things that needed verifying/addressing. I measured the points and found them to be at ~.53mm. Adjusted them back down to ~.35mm. I then readjusted the timing (statically.) Here's a video showing those results:
http://s13.photobucket.com/user/nduetime/media/kz400/2.mp4.html
So at that point, I managed to drop the rpm's a bit but it was still very high. Turning the idle adjustment screw didn't change anything. All the way in or all the way out, no difference. I decided to stop for the evening to allow myself time to process the situation. I knew from Saturday that there's air leak/s at the manifold/boots. Given the bike races and doesn't retreat, I kept thinking it had something to do with the cable. However it has plenty of slack and isn't kinked. The more I thought about it, the more I was certain it had something to do with the slide staying open.
I spent 6-8 hours reading and watching videos on issues like I was experiencing. I found myself going back to the PWK carb diagram, which I've been studying for the past week or so. I kept thinking, what would cause the slide to stay open and not retreat? Stuck cable, improper idles adjustment screw position, faulty spring. Then it hit me...if the spring compresses and doesn't return, the slide won't return to where it needs. I knew from looking at the diagram the spring contacts a collar at the carb side. I remembered mine didn't have one when I took it apart. The collar plays a vital role. The more the throttle is engaged, the more the spring is compressed. Without that collar to keep the spring end stationary, the spring continues to jam down inside the slide, resulting in the slides inability to return to being fully seated.
After work today I decided to put my theory to the test. I cut out a "collar" (basically a couple of washers) from a plastic water jug and placed them between the spring and the cable holder and reattached the cap to the carb. Here is the result:
http://s13.photobucket.com/user/nduetime/media/kz400/3.mp4.html
With my makeshift collar in place, the spring is unable to seat down into the slide and allows the throttle spring to compress and extend properly. With a much more manageable idle, I was able to play with the idle adjustment screw. Doing so resulted in being able to adjust the idle up and down.
So, a very small discovery that is probably a given to many others was a large accomplishment to me. Super excited now. This is going to be a fun ride!
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Vintagehonda750
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welcome to the forum
