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Discussion Starter · #1 ·
ok guys, getting the bike all back together, took it for a quick spin before I put all the bodywork back on, when I notice an issue. it doesnt seem to matter what gear I'm in, if I've got the throttle wide open, the engine bogs out at about 4500 RPM, it will come back at about 3800RPM, but will never hit the red line if I mash the throttle wide open. HOWEVER, if I roll up on the throttle gently, I can get up and past the redline.

pulled the top off the air filter box and it seems to walk right up to the redline without issue, but when the air filter is re-installed and top of the box back on, the problem returns.

a little history, I just had the entire engine out of the bike due to a shifting issue (shifts just fine now) and had the carbs off. when I had the engine out, I changed the timing belts (have a small chirping noise coming from the front of the engine at idle too) new fuel filter, new air filter.

I seem to remember the engine bogging down on a ride before I took everything apart, so I dont think that anything I did could be causing the problem.

pretty sure I put the filter in right, going to check on that now and while I'm at it, will check the fuel pump pressure
 

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Discussion Starter · #4 ·
didn't think to blow through the filter, I've got it installed in the right direction, full tank of gas, fuel pressure just over 2 PSI. haven't tried again with air filter off, but on the center stand, in neutral, dumping the throttle wide open the engine runs up to just under 5000 RPM then the RPM's are up and down, I guess I'd describe it as a 'flutter' almost.

I'm stumped
 

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Discussion Starter · #6 ·
ok, no resistance blowing thru the air filter, vacuum gage on the automatic fuel valve shows total loss of vacuum when at wide open throttle, RPM's no higher than 4750. applied external vacuum to the automatic valve, same result. looks like time to double check vacuum lines and timing belts

:headbanger:

this project has felt like one step forward and two steps back for the last couple weeks now!!!
 

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Discussion Starter · #9 ·
valve holds vacuum rock solid, all good there, going to do some spraying around the carbs to see if I have a vacuum leak, got some sealing grease for the boots, I have a feeling those are the issue
 

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Discussion Starter · #12 ·
ok, now I'm really getting frustrated. fired bike back up, ran the RPMs up to the "trouble zone" and blocked off airflow with my hands, RPM's dropped even further, so I tried spraying carb cleaner in the throats at idle, RPM's dropped again. I think that I can then assume that I have no vacuum leaks. I sprayed carb cleaner around all the vacuum connections with no increase in RPMs again, so I think vacuum leaks are not the problem (damn)

pulled the timing belt cover off, found the right belt a bit tighter than the left belt, but timing marks lined up perfectly. re-tensioned the belts, fired it back up, now I get up to about 5000 RPMs before we start losing RPM's again.

the heat riser snorkel is operating correctly, although for most tests the cover and the air filter were removed from the air filter box, so for the most part we've eliminated that as well.

I'm beginning to wonder about a couple things. First, the carbs were off for a few weeks, wondering if the floats are hanging up somewhere due to being dry for so long. on second thought, the fact that I can gently roll up to redline but a sudden opening of the carbs gives me the RPM loss doesn't seem to make sense either.

I thought that the Idle Airshot System might be malfunctioning, but I would assume that would give me a lean condition at high RPM's and partially blocking the airflow would give me a rise in RPMs rather than a drop?

any other thoughts?
 

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Discussion Starter · #14 ·
true, very true.

just for kicks, I tested the Idle Airshot system according to the service manual and it passed.

also for kicks, I took off the air box entirely from the carbs and rapped on the tops of the carbs with a screwdriver handle, just in case anything was hung up, figuring the vibration would help knock things loose.

interestingly enough, when I put it back together, it seems to rev higher without cutting out.

I'm going to put the timing belt covers back on tomorrow and take it out for another quick ride and see if things behave, or if I still have gremlins plaguing me (I even put the bells back on today too :p )
 

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Discussion Starter · #15 ·
tried taking it out for a ride again today, same problem :(

"just to see what would happen", i closed the choke when it was cutting out, and...........nothing happened, no rise, no drop, no effect.

I tried rolling gently up to 6k when the engine began to miss!!! I started pulling plug wires, noticed that the front left cylinder (#2?) was not firing, but after a moment or two, began to fire again. :wtf:
I'm pretty sure the gear selection switch is working because I get a neutral light and the OD light comes on in 5th, so I don't think thats an issue either.


looks like I'm gonna pull the carbs (again) and apply grease to the boots, just in case they are leaking and double check all my vacuum lines, I also have a small water leak down at the pump that will require a new hose, so gonna do that as well. Also gonna replace spark plugs tomorrow.

I'm wondering if the ECU on the 1500 needs to be reset?? does it hold any settings that might be limiting the revs?? gonna disconnect the battery while I'm working on the rest and see if that makes any difference.

has anyone else ran into this kind of issue on their 1500?
 

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Discussion Starter · #17 ·
interesting, is that 5.5k in neutral and 6.5k in gear? I've never hit any sort of rev limiter before.

I do have a different hear indicator switch in the engine (I broke the old one, this one is used), wonder if I need to jump some of the pins (making the bike think it's in 2nd or 3rd gear) and see if I still hit the limiter. I have the same RPM falloff in every gear.
 

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Discussion Starter · #19 ·
mine is cutting out at about 4.5k, sorry if I mislead anyone thinking it was a 5.5k, if I dump the throttle open, it cuts out at about 4.5k, if I ease into the throttle, it will go up to redline.

before I tore into the bike, it would go over 100mph no problem, now it has a hard time doing 75

also, before the repair, first gear acceleration was neck-snapping and I loved it!, would run right up to 5.5-6k now it seems to be way more sedate, I know it's not the gearing, clutch isnt slipping, all power is gone at about 4750 rpm, if I keep the throttle open, it will lose RPM's down to about 4200 before picking back up, going up to about 4500rpm but not running well at all.

Both slides appear to be working correctly, they are open about 1/2 way before the engine starts cutting out. I tried manually holding the slides open all the way, and still have the same RPM issue
 

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Discussion Starter · #20 ·
took carbs off, greased the boots, put it all back together, same thing, cutting out at about 4750rpm, bogging down to 4200 then coming back up.

I dont have a timing light to check if the timing is advancing/retarding correctly, is it possible that is the problem?

I also noticed today (don't ask me why it took so long to notice), that I smell unburned gas from the exhaust when it is cutting out.

Soooooo, I'm now thinking its something in the ignition system, will replace plugs tomorrow and get a timing light to check it per the service manual.

any other input would be most appreciated!!

Kaz
 

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Discussion Starter · #24 ·
oh hell, is it possible that diaphragms or other carb parts dried out when they sat on the bench for a month? the slides look like they are working ok (they are moving at least)

is there a high speed jet that is used primarily at WOT that might be clogged?

I'm gettin close to chucking parts across the garage already!!


AAAAARRRRGGGGHHHHHH!!!!!!!!!
 

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Discussion Starter · #26 ·
thank God someone else has this problem, what you describe is EXACTLY what is happening to me!!!!! I was getting set to order rebuild kits, but will hold off for now. I assume that you have checked your timing belts as well?
 

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Discussion Starter · #27 ·
breakthrough? maybe?

pulled the top of the airbox and the filter, engine hit 6k on WOT!!! put air filter back on, and I get no more than 4750 again. lifting up the air filter a little bit at WOT while bogging down, the RPM's came up!!!!

This is a brand new air filter, so I'm pulling the carbs (again) to see if I can find a vacuum leak, my thinking is the resistance from the air filter is allowing air to leak somewhere between the filter and the intake.
 

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Discussion Starter · #30 ·
I think I found it!!!!!!

pulled the carbs to look over all the vacuum lines, noticed that there was a dark spot on the line going from the IASA check valve to the intake (hose number 11) under the rubber mat. closer inspection revealed it was a HOLE!!!!

must have gotten too aggressive with the pliers when I re-assembled it and pinched a hole in the hose. I'm not sure a small hole like that could make a difference, but I'm off to Autozone to try to find a suitable replacement and put it back together and let you all know!!!
 

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Discussion Starter · #31 ·
it would appear that the nick in the 11 hose on the front of the intake (going to the IASA check valve under the black mat) was contributing to my issue!

now I have to pull the carbs back out, because I have fuel running out the top of the Left carb!!!

This bike is turning into a game of whack-a-mole!!!! I will prevail!!!!!

Kaz
 

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Discussion Starter · #33 ·
I believe it was because I had the air filter off when I sprayed, also, this hose is under the famous rubber mat, so it's really hard to get anything under it when checking for leaks
 

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Discussion Starter · #34 ·
FURTHER BREAKTHROUGHS!!!!

After looking at the timing belt tutorial on this site last night, I didn't realize there was a timing mark on the crankshaft pulely closer to the engine, I had been lining it up from the mark on the end of the pulleys. When I lined up to the "inner" mark, I found I WAS 3 TEETH OFF ON BOTH SIDES!!!!!!

pulled apart the crankshaft pulley, found the last part of the pulley has a small teat on the back of it that goes into a groove in the end of the crank. Someone before me must have not lined it up when they bolted things back together.

Thankfully, I've been careful to rotate the engine several times with the spark plugs out to check before started it!!!!! I shudder to think about crashed valves!!!

I've put the crankshaft pulleys back together correctly now and corrected timing, I'll bet it runs a lot better when I put the plugs back in and fire it up!!

Kaz
 

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Discussion Starter · #35 ·
a quick ride after putting the plugs back in and checking carb sync gave good results, felt like it popped the front end off the ground when I hammered the throttle in 1st gear, definitely popped it off the ground when I hit second just south of the redline
:jumper::jumper::jumper:
 
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