|Topic Review (Newest First)|
|05-12-2019 07:28 PM|
Yep. Got it figured out (the FPR too) with help and advice from you guys. And yeah, it's a little irritating when someone asks for advice or help, and you never hear from them again. Figured the courteous and decent thing to do is fess up, swallow my pride, and post how it turned out.
While I had it out, I did take advantage of the situation, and thoroughly lubed the cables, and cleaned the throttle body throats (just sprayed some throttle body cleaner in there - didn't scrub anything), inspected the vacuum lines, but didn't replace any of them, etc. If I ever need to replace the starter or remove thatA whole assembly again for any reason, I know I won't have a problem doing it, so that's cool.
Speaking of cool, I finished flushing the cooling system today and filled it with fresh 50/50 coolant. Figuring it's 17 years old and has 73,000 miles on it, I figure it wouldn't hurt to flush in and put in fresh stuff. I used a cleaner that's supposed to be safe on all vehicles and all metals. Mixed it with distilled water and ran it since last weekend since just before this fiasco. Today it drained out gray and dirty. I filled it with pure distilled water, ran it, let it cool, drained it, etc, over and over until it came out clear today, then filled it with green ethylene glycol, long life, all metal safe, motorcycle approved 50/50 antifreeze. Still running great. Glad to have it back in shape.
Mcromo, I can't think of a "worst BIKE blunder" off hand. I'm sure there are some, like getting the carburetor rack installed back in a bike, then looking over and seeing the slides and diaphragms sitting off to the side, etc. (I think I remember that really happening). The worst blunder EVER, though, was many years ago (maybe 20) with a 1984 Ford Bronco II. It had been overheating, and I wanted to replace the thermostat. While trying to get the top housing off that the big hose was connected to, on top of the intake manifold, I twisted off a bolt head. That bolt goes right into the intake manifold. I managed to get the other bolt out. Got the housing off. No thermostat. What? Every thermostat I've ever replaced on every engine since the beginning of time, is under the top hose housing on the intake manifold. Not this one. On this vehicle, it's under a housing on the FRONT of the motor. So all that for nothing. F***! Alright. I'll get one of those hardened steel "Easy Out" things, drill a hole in the remainder of the bolt in the intake manifold, and back it out with that. Drilled a hole. Got the hardened steel "Easy Out" tool in there nice and tight... and broke it off flush right flush with the headless bolt. FML. I had to replace the whole intake manifold. And I shouldn't have even been messing with that part in the first place. Leave it to Ford to put the thermostat in a whole new place. That was NOT a fun lesson. The thermostat, by the way, was easy as pie and went very well, after I read the service manual. (I think that was before the internet really took off).
|05-12-2019 07:38 AM|
And compared to some of the lessons others have learned, myself very much included, your's was not as painful as some are.
A couple of times in the past, I have pondered starting a thread called "your worst blunder working on your bike", but decided against it. At least now I can laugh about my follies. Hopefully you will be able to laugh about yours too. Hey, at least you figured it out!!
|05-12-2019 01:48 AM|
Clean and check everything.
Good call on the vacuum hoses. The stuff is cheap.
Careful cleaning the throttle bodies. Only clean the outside. There is a coating on the inside that should not be removed.
|05-12-2019 12:49 AM|
I think we've all done something like that, glad you got it figured out and didn't have to replace broken parts.
Maybe a good time to clean and detail the engine, maybe even check the valve clearance and the pairs mod while you got to torn down that far.
At least take the time to look for cracked hoses that might need replacement.
|05-11-2019 06:02 PM|
Lol.... I had a feeling something had got sucked into the Butterfly valves but what?
Probably a good thing it got caught there and wasn't sucked in further. Who knows what havoc it could of created further into the engine.
What an excellent opportunity to clean all that area up.
Well done on sorting that out and thanks for the follow up. It sux when there's no ending to a story.
|05-11-2019 05:13 PM|
|badrad600||It wasn't near as bad as I thought it would be. Problem solved. Pry bar from Harbor Freight. A little time and patience. No big deal. But... all this could have been avoided. Remember I said I had to soak up all the gasoline out of the airbox when the fuel pressure regulator failed? Laugh if you like. Slap yourself on the forehead or shake your head and say "what a dumb****"... Flame me if you want. But... lesson learned. Actually I learned a lot through this whole ordeal. It wasn't so bad. And, I'm glad it was an easy fix. (Well... not exactly SUPER easy, but nothing was broken or needed to be replaced.) Thank you for all of your input and advise. Anyway... for your entertainment and enjoyment, here are some pictures of my day.|
|05-08-2019 09:14 PM|
A 450mm or 500mm tire lever would be the perfect tool.
I wrapped mine in tape just so it wasn't so hard.
Good luck. Have a beer and a swear jar handy!
|05-08-2019 08:33 PM|
Thanks for the link, Islandboy. I'll try a crow bar this weekend.
Grgmini, I have the throttle tube off the handlebars now, and the cables removed from the throttle tube housing. They look to be where they should be, down at the throttle body. I'm stumped. I don't know what could be jamming it open. I'll probably go through all the trouble of getting the throttle body out, and it will turn out to be something really small and stupid. I'm pretty determined to get that thing out this weekend and finally find out what it is.
|05-08-2019 05:21 PM|
I had something similar happen to me recently with my BMW K1200. I hadn’t set a cable end in correctly (that bike uses an equalizer) and it idled fine at first, but when I revved it he first time, the engine raced and would not come back down. I also just had all of that apart on my 919 and had to play with the handlebar end and throttle end a few times until I was happy with it.
Maybe the return cable is hanging up? Is it routed correctly at the grip?
I would start with loosening the cable adjuster at the throttle and see if it closes. Check the return and routing at the grip.
The throttles shouldn’t have to come off, but spraying a little soapy water will help if you do.
|05-08-2019 12:43 PM|
|Islandboy||This thread might help... Airbox/Injector removal https://www.wristtwisters.com/forums...ad.php?t=77897|
|05-08-2019 12:36 PM|
|badrad600||That's what I thought too. Looks like that part belongs on the end of a copper tube. Have a late shift today. Decided to look at the bike. Got it all apart again, wires disconnected hoses out of the way, airbox bolt out, and the engine side clamps loosened. The manual says remove the assembly by separating the boots from the engine side. I can wiggle the throttle body / airbox assembly, yank, pull, twist, whatever... those boots aren't budging a hair. There's maybe 15mm, or 5/8 to 3/4 of an inch of play behind the airbox. I can move the assembly up and down, but pulling back does nothing. Those boots are on there hard. I'm tempted to pry and cut them off and replace them when done, but don't want to damage anything else. I loaned out my heat gun, so I can't do that. May not be a good idea anyway. I'm getting too old for this stuff. Eh... gotta get ready for work now. I'll take a crack at it later. After all that moving around, I checked again. Still not closing. idk.|
|05-07-2019 10:35 AM|
Originally Posted by badrad600 View Post
As for my mild build, the idea was to get to where the 71s were, plus a bit more by detailing (port and valve work) and a bit of added compression ratio.
|05-07-2019 09:26 AM|
Haven't removed the cables at the throttle body end. I haven't even been able to see where they connect yet. I've read that even that is a very challenging task. I'll probably invest in an articulating mirror. Harbor Freight would probably have something like that. I also have a good, bright led flashlight, and some reading glasses, for if I'm wearing contacts. Don't know how old you are, but my eyes aren't what they used to be, either. I turn 50 next month. Others here are probably thinking now we need fast wheelchairs instead of fast bikes... lol.
And wow... sound like your CB750 is more than "mildy modified"! If that's mildly modified, then I guess my Yamaha Radian is mildly "messed with"... ha ha.
By the way... about to go to work, but poked around in there again a minute ago, and found this brass nut sitting on the engine case below where the throttle cables would connect to the throttle body. It was sitting right there at the butt end of the starter. I'll try to attach photos. I don't know what this thing is, or where it goes.
|05-07-2019 08:24 AM|
Originally Posted by badrad600 View Post
If you haven't, suggest you do, then it's a for sure that nothing inside the TBs is at play.
If the TB shaft still won't close to rest on the stop, then maybe you can get a small articulating mirror to go in the air box with the filter out and perhaps be able to see something.
You'll need a good small flashlight for that, my old eyes would need a LED bulb for sure!
As for the needles on my old K, I was flabbergasted by the effect of the change, but the distance from one groove to the next is pretty major - I didn't know about shimming back then. The engine is cammed, has 75 SS pistons in it, custom multi-angle valve job (winter '74/'75 build), some port work with some D shaping as part of it, revamped carbs with early K emulsion tubes (main jet holders), changes to pilots and mains and idle bleeds. Pipes are early K with secondary baffling removed. I need to resurrect it, it's been parked since '95.
|05-07-2019 05:57 AM|
|badrad600||Yep. That's what I was seeing. The two screws are not touching. As shown in your photo, on my bike, the screw on the left is not touching the brass pad, and the screw on the right is not touching the metal arm. I am hoping it's external, and I'm hoping I can find / see what the problem is without removing the whole assembly. I wouldn't think anything made its way all the way up into one of the intake ports in the airbox and wedged between a butterfly and throttle body, but I suppose anything is possible.|
|05-06-2019 09:24 PM|
I think you're on the right track. Something has made its way into the throttle workings and preventing the throttle/butterfly valves from fully closing.
The pic shows how things should sit at idle. Either something is jamming at the external mechanism or perhaps from the inside. Could it be possible for something to get sucked into the Butterfly valves and jam there?
|05-06-2019 07:49 PM|
Thank you all for your input. I appreciate every one of the responses. Everyone is really cool in the Yamaha group. I can tell you guys are, too. I've read some posts on other forums, and sometimes an innocent guy looking for help can get flamed hard by a bunch of ruthless guys. That's not the point of a forum.
In any case, today after work, I went out and took the cables out of the throttle control. With the throttle cables completely out, I lubed them and worked them in and out and let the thing snap shut a lot of times. With a flashlight, I looked from the right side of the bike, as best I could, to see what I could see. I am pretty sure I can see the stop screw and the throttle wheel, or whatever it's called that's supposed to engage it, is not quite getting there. I can pull the pull cable, and the part that is supposed to engage the stop screw moves up and away, but when I let it snap shut, there's maybe 3mm, or a little over an 8th of an inch of space between the stop screw and what it's supposed to stop. So........... there's obviously some kind of blockage somewhere preventing the thing from snapping shut all the way. I'm pretty convinced of that.
Now my daunting task is finding out what's in the way and where. I wouldn't think something made its way into the airbox and all the way into the actual throttle body while I had the filter out and all that. It must be something I did, or a little part that dropped down in the works around the the throttle body, externally, while jacking around with all the stuff I did with it all apart. I had the tank completely off multiple times, the radiator dropped out of the way, the coil for 1 and 4 removed so I could change the plugs, etc, etc.
I just went out there and looked again. Looking from the left side, it appears there are two stop screws, neither of which are engaged, and 2 to 3 mm of space. These are on the bottom of the throttle body, way deep in there, between 2 and 3, with a bit of white paint on them. Given the fact I let that thing snap shut so hard so many times, and it still won't close all the way, something solid must be blocking that thing somewhere. I did take a long screwdriver and worked the spring throttle wheel open and let it close, and then tried to force it closed it all the way. I could get it closer, but it would then go right back to the 2 or 3 mm of space. This weekend, or as soon as I get time, if I can't find the problem by slowly and carefully inspecting everything, I'll pull that freakin' throttle body airbox assembly all the way out of that bike and figure it out. I don't want to, but I may not have a choice. Someone put that thing in there. Someone can take it out. Unfortunately, that someone will be me, and unfortunately, I don't know any mechanically inclined people in my area to help. Thank you guys for the support and ideas. I'll keep you posted.
Btw... Mcromo44 - I'm surprised raising the needles one notch / step jacked up your idle like that! I have Dynojet needles in the Yamaha. It took a long time to get everything just right, with it mildly modified. The pilot jets are one size up. The mains are two sizes up. The exhaust is a Kerker 4 into 1, and the airbox is intact, with a small hole in the rear. The needles are ... seems like second to the top notch, with little shim washers to get it just right. It took a long time to get all that figured out just right. The bike was all jacked up when I got it. It was quite gratifying when it all came together and it was finally spot on, but it was a lot of tedious work getting there.
|05-06-2019 05:24 PM|
Originally Posted by Islandboy View Post
And for his sake, Choke = Starter Valve.
|05-06-2019 05:17 PM|
There could be a combination of things involved.
For sure it's an odd one.
|05-06-2019 05:00 PM|
|KarlJay||Great call on the vac lines. I was under the impression that the bike idled properly, then once you revved it up, it would stick. Maybe something opens and then the vac leak happens.|
|05-06-2019 03:34 PM|
The engine's got to be getting air from somewhere.
Vacum hose off or broken on throttle body? Could the choke be on?
|05-06-2019 10:26 AM|
This is a very odd sounding situation.
Especially reading that the cables have since been proofed.
Seeing as things were A OK before the mechanical work, the highest probability of cause is a consequence of the work just done, noting the tank had to be up, or off for that work.
So, I'd suggest eyeballing and checking things extremely carefully in an all encompassing way with the tank back up and see what that reveals.
IF your butterflys are properly closing through a full arc of handlebar sweep, then the ONLY way you can get high idle speed is from unintended air and/or fuel.
The salient point here is that just because the butterflys are closed, does NOT at all mean the engine can't be revving much higher under no load.
A few things to check or consider:
Check the idle stop screw for contact on its register, as it is an absolute indicator of butterfly shaft position.
Check the Starter Valve actuation train, to make sure it is not engaged.
Check all vacuum lines.
Check the TPS.
(To explain why, consider this: Back in the 70s I was doing lots of carb tuning on my mildly modified SOHC CB750. When I tried raising the needles by one step, the bike idled at 4000 RPM.)
I sure hope it's something basic and not TPS related.
If you're lucky, it will be so and easily fixed, and I have a feeling your chances of that are decent.
You've done a pretty good job at assessing, but a bit more is needed.
Assessing being step one of the Assess/Diagnose/Prescribe problem solving model -and never change the sequence or jump to the next step without fully completing the prior step).
Plus never forgetting that a new problem immediately on the heels of work completion, is by far most likely a result of the work just completed.
|05-05-2019 08:37 PM|
You're right about TB being closed will keep the engine from revving up. I'm guessing you can't see the TB being closed. If you have a good visual on it, then I'd suggest that you really can't see the amount of movement that is needed to cause the RPM change you describe.
I would take the cable ends and get a feel for how free they move. I'd do a flood of light machine oil down both cables and look for a solid snap back.
You should be able to get in there and see the idle screw and if the TB is touching it.
1. Cause it to get stuck
2. kill the engine while it's stuck open
3. reach in with a screw driver and force the TB closed (verify this by starting the engine again and seeing if it's truly idle)
If you can repeat this, you'll see exactly how far it's open.
Fully lube the cables and see if that gets it to snap back.
You could have a butterfly that has moved and it causing friction or you could have something like a broken return spring or something stuck in the linkage area like a rock or twig.
I assume you've removed the cable ends and can operate them without the hand control by just pulling the ends. If that works, I'd also look at how much friction there is in the hand control.
|05-05-2019 06:24 PM|
Throttle Stuck Open
Hello again, guys. I'm stumped again with another issue. I replaced the fuel pressure regulator, drained the crankcase, put a new filter and fresh oil in it, pulled the plugs, turned the motor over to blow the fuel out of the flooded cylinders, put in new iridium plugs, and flushed the radiator. I also replaced the fuel saturated air filter with a freshly oiled K&N filter. It started and ran fine for a while. It ran great, in fact. As I was going for a short ride this weekend, I goosed the throttle for a grin, and the grin went away pretty quickly when the engine stayed revved up. The bike wanted to haul ass, and no amount of whacking the throttle back and forth would get it to come back down. That made for an interesting and nerve wracking ride home (maybe 3/4 mile or so- kill it, coast, stop, fire it up, go, etc). Anyway, after jacking around with the throttle cables and checking the routing and everything, I pulled the throttle assembly all the way off the handlebars to play with the cables and make sure they were intact and moving as they should. The throttle snaps back as it should when released, and, if I look way down into the throttle body area, I can see the little wheel rotate as it should. It seems to snap back right to idle position as it should (visibly and audibly). However, when I fire up the bike, it wants to rev to maybe 5 or 6 grand. If I crack open the throttle, it revs higher, but doesn't come back down. It seems to me that if the cables seem to be moving as they should, and the wheel they're attached to on the throttle body is moving as it should and closing as it should, the butterflies in the throttle body should be physically closing, and it shouldn't be able to stick open, and the bike wouldn't be able to get the air intake needed to rev that high. I've searched the forum and the internet and clues, and haven't found much helpful information. If the TPS were faulty, it shouldn't be able to rev up the bike, if the butterflies are closed and it can't intake sufficient air. Apparently the TPSs almost never fail anyway. So... at this point, I suspect I may have to attempt the dreaded deed of pulling out that whole throttle body assembly, checking everything, maybe installing new cables while I'm at it, etc. Or I could just try replacing the cables and that's it- still a challenging task. Pulling the carb rack on the Yamaha 600 isn't really for the faint of heart the first time, but I've done it so many times, it's no big deal. The 919, however.... well, that looks a good bit more intimidating with all the vacuum lines and sensor connectors, and probably even less space to pull back the box and work it out the left side. I'm not really scared to attempt it. I just really, really don't want to, if it can be avoided. I know it will be a major pita. So... any ideas? Just wondering if there's a common thing that may cause such an issue, like an idle air valve or something. Thanks in advance for any input.