Clutch/Trans knocking in Neutral? '86 750

Ok, So without worrying about sounding like a stupid ass newbie - I've got a question to ask, and I pose it to you guys & gals cause I'm not understanding the "Why" of it happening, or the "How To" of correcting it...

When I start the engine (which it does without any prob on the 1st shot now that I've got the carb completely fixed) and the clutch is pulled in (disengaged) it idles fine. When I let the clutch out to engage it (in Neutral mind you) it makes a tapping/knocking sound at the low end of the motor, more to the right side but can be heard from the left. There is no physical tapping against the block itself that I can feel. The clutch fluid was just changed out a few weeks ago with fresh DOT 4 synthetic, and I'm pretty sure theres no air in the line cause it was done exactly the same way I flushed out the brake lines.

Now, on idle with no choke it'll stall out if the clutch isn't pulled in (in Neutral still) but if it's disengaged all the way there is no knocking/tapping and it idles fine. To be clear: No clutch + idle @1200 rpms = stall / Clutch in + idle = fine

I did notice that it will maintain idle without the clutch and in Neutral if the choke is about 1/4 engaged, basically the extra fuel compensates and overcomes the drag on the motor by whatever is causing the tapping.

The bike shifts through all the gears perfectly, no hang ups, no slipping...

I don't understand basically because there is no way, according to the manual that I am looking at, to adjust the clutch other than the handle itself - so I'm assuming that it's a 'self-adjusting' system with constant pressure against the clutch pressure plate and that the fluid level is what would be the adjustment in the system. The fluid level is just fine.

And just for the record, I've gone over this several days in my head and asked a few choice people that I thought would know the answer, but after they've proven themselves wrong on several issues that they were certain of before they, don't want to assume the wrong answer again... basically I've covered more in school than they currently know and the questions I'm asking now are more along the lines of "I'd just take it to the shop" attitude from them.

Things I'm thinking it could be:
1) Bent shift fork
2) warped plate
3) clutch out of adj

Anyone care to try on this one? All guesses will be considered.

 

the fluid doesnt do anything but engage/disengage the clutch via a rod, your clutch is bathed in motor oil. That being said there very well could be air left in the system given thats the last thing you changed prior to having the issues. If that isnt it, and assuming you are using motorcycle oil in the engine and not auto oil, I would check the plates next and then the clutch basket itself. The plates may be getting hung up on the basket. But in my experience, it's the last thing you touch that is the culprit.

 

sorry it's been a while since I've been on here again. I get so busy doing the least significant crap lately!

According to my Clinic 3 Instructor, Gary... who's been working on bikes professionally for 30 some-odd years... without going into detail about what I've done to the bike at all I just told him the symptoms of it knocking/tapping in the lower end and a noticeable difference in sound when I pull the clutch... his quick reply:

"Your carb is out of sync, Harry. Your pistons are trying to move while the others aren't and it causing them to fight one another, which is causing them to hesitate for a moment. What do you think that's doing to your lower end?"

I thought about that a moment and replied "It's making the crankshaft vibrate which would make everything attached to it resonate and move against the adjoining parts."

To which he replied "Yup, and that's your tapping noise. Sync your carbs and no more noise. She sputter and kick a little bit when you get on it from a dead stop or a slow crawl?" I nodded "But on the mid range and high end she's fine?" again I nodded "Then take your bike over to Clinic 5 or 7 and get em sync'd, unless you like not having that extra 10 hp and blowing 5-7 mpg out your pipes every day" said with a shit eatin grin cause he knew he was right.

I then told him about the carb rebuild and he was quite impressed that I did it all without breaking anything major that couldn't be fixed (still feel like crap about the plate incident). Showed it to him and he said it's been a long time since he's seen an '86 in that good of shape and sounding that good without being completely rebuilt.

That made me feel good. SO.... the issue still is the sync and it's not the clutch or the trans... being as I don't run city streets and 99% of my travels are at speed, I got the green light to keep running it, but it will be fixed by the end of the week (my temp tag expires on the 29th so I gots to have the emissions done before then)

Thanks for the replies, now go out there and enjoy the great weather!!!!

 

YES, a poor synch setup causes small fluctuations in engine speed, and that knocks clutch plates back and forth within the basket=noise.

When the bike's idling in gear while you squeeze the clutch, does the rear wheel spin forcefully or can you stop it with a little friction ??

Do you have trouble getting neutral from any gear while engine is running ??

Didn't you claim the carbs were already synched properly by MMI professional instructors ??

 

Knocking noise comes from the dents in the clutch basket...if you'll make a carb syncronization probably your engine will be smoother but the knocking sound will still be there...100%

 

I haven't tried putting it on the stand to test the neutral anti-spin or in gear clutch stop. I'll check on that tomorrow morning. There is no trouble shifting in any gear up or down. And as for the carbs being sync'd prior, yes the bike was brought in to be sync'd but because the slow jets were still clogged it couldn't be done properly. They were not bench sync'd prior to the last re-install so they are way worse than before as far as being one unit as a whole. Last week was performance week, so I wasn't able to get it in to be checked again since everyone was doing projects and tests (including myself).

 

I am having the same issue...So if he replaces the clutch basket with a new one, then the noise should go away?

 

Beta,

I dont see what the difference between moto oil and auto oil is.Can you please explain...I heard the same thing but I am not sure why auto oil would be an issue...

thanks

 

Barnett clutch's back in the day had very thin fingers and were prone to wearing into the basket in a very short period of time, given the age of the bike it is very likely that it may have had one installed at one point and is a sloppy pig. A quick inspection is in order I think.

 

Well, it's time to lay the knocking noise and carb issues to rest! Yay!!!

I've gotten TONS

 

Well, it's time to lay the knocking noise and carb issues to rest! Yay!!!

I've gotten TONS of input from many people over the past week or so, checking this - checking that. Some of which was useful and very insightful, and others that were pretty much reaching based on past experiences with similar motors. A few were warranted enough to try and I did so, but each 'test' produced no result and there wasn't enough consistency to preclude a diagnose. I finally had enough and this morning I pulled her apart... again... for the 4th time. It struck me while I was in the shower the night before that if the throttle plates were moving 1/4" delay from one another that there had to be something missing and that maybe, just maybe there was something that myself and everyone else who has worked on this bike the past 2 months simply overlooked. I was determined to find the problem and so I set to it.

After pulling the seat, tank, air box and carb off, draining the fuel from the bowls and then flipping it over to give it a thorough inspection I noticed something immediately out of place. There was a spring that fell off (literally without force) when I was cleaning it the first time. It was one of the lower sync springs and I found where it went next to the other set that was next to it. I thought nothing of it at the time, and therefore... no other parts laying around and unaccounted for after reassembly I left it at that. BUT... there was the carb sync adjuster screw on the opposing side of the carb, the single unit that controlled the remaining balance of the throttle plates. I peeked underneath of the screw and sure enough, the spring was nowhere to be found. I very easily plucked one of the other lower springs from the main side and headed to the computer to find the part number.

A quick trip to Apache Honda to see about getting a few springs proved futile. Seems that this too (of course) is a limited availability part and that it had to be shipped - not from California - but from JAPAN and that it would take 2-3 days to arrive via air mail for a whopping $5.50... for a 1/2" long spring... yeah, no thanks. I decided to try my luck at a hardware store after having luck with the float bowl gasket earlier this month. Low and behold, I found a pack of 6 springs with the same rate and just a tad longer than the original for $3.50!

I went home, replaced the one and then decided to take a peek at the remaining springs and decided that 24 years had taken it's toll on them so I replaced them with the new ones, trimming off about a full turn from the new springs. They fit perfectly and the throttle plates all moved in unison.

After a few yahoos and hoorays I then proceeded to do a bench sync, turning each in fully and then out 4 turns each. I had cut a 1/2" wide sliver of paper and opened each throttle plate to test it's feel. They were all about equal in drag, so I figured that was a good place to start from. I quickly reassembled the bike - taking care to properly adjust the choke and throttle cables - filled the bowls and then opened the choke wide and hit the start button.....

She fired right up, and hit 2200 rpms right off the bat. I let her warm up to just within normal and dropped the choke. A quick adjustment of the idle screw brought her from a low 700 rpms to 1200 rpms and she maintained that without hesitation and 0% choke. I hit the throttle a tad and she roared like I'd never heard her before - super quick throttle response. This had to be celebrated with a trip around the block!

I backed her out of the driveway and headed toward the main road in the development, started to lean into the turn and hit the throttle a tad. Now normally at this point she'd start to pick up a bit of speed but was always like "OK, if you insist..." but this time she damn near threw me off the back end of the bike! I've taken the back seat cover off the bike mainly for looks cause I wasn't very appreciative of the seat covers function rather than the looks. I immediately turned the bike around and returned to the garage to reinstall the cover. Back at the same turn and the same amount of throttle that I always have used again and my ass was tossed into the butt cushion of the seat cover and the front end damn near lifted off the ground! Can you say "Holy Shit!!!!"

Needless to say, this pretty much told me that she's back to healthy again, and ready for emissions testing. Oh, and for the record: The knocking/tapping noises = GONE, completely and 100% quiet. You can hear the piston travelling up and down, and the slow whir of the gears at the cams, but aside from that she's quiet at the front end now. Shifts beautifully through every gear - up to 6 and back down with no rattling or pinging of any sort. I'm still planning to do a valve adjustment in a few months after I get to work on the V45's in school and know wtf I'm doing 100%, but I don't think that it's much of a major thing right now. And also while I had the bike apart, I pulled the plugs and peeked down through the intakes and the plug holes to see how the piston and cylinder were looking inside... the bottle of Techron concentrate that my instructor recommended over 5 tanks definately did the trick. Theres just a light bit of carbon on the top of the piston and barely any on the valves now, whereas when I first got her it was like viewing stalagmites and stalactites in a cavern. That just made my day that much more!

I'll be taking her down for emissions testing in the morning and then straight to Motor Vehicle to get her permanent tag. Thank God this damn thing is over. 2 1/2 months, and the whole time it was because of 1 tiny little fucking spring, and 2 others that had lost their rate to the point of uselessness. I bet the one spring that was missing had fallen off prior to me even getting the bike!

 

Emission tests on Bikes in AZ?

 

The valves should have been adjusted first, you finish every tune-up with the carbs last for future reference.
I still have some carb issues that I have to work out myself here, I'll be buying some new intake insulators first though.

Good to hear you sorted your carb issues out.

 

Due to high population and poor air quality, Maricopa County has emissions testing on any motorcycle from 1966 and up, and all vehicles 1981 and newer. In most cases its every 2 years.

 

The point made about not using automotive engine oil was that it contains high amounts of detergents and additives that can break down internal parts and cause extra unwanted friction inside your bikes engine. The reason being is that in your car your trans is seperate from your block, hence why you have ATF fluid or manual trans lube. In a bike its all one unit, the oil not only lubricates the crankcase, pistons and valves, but it also lubricates the clutch and the gears in transmission. The more lubrication, the better it will perform... to a point. Too slick of oil will prevent certain parts from operating properly as well. Thats why certain oils were designed specifically for bikes, to reach that balance of not too slick, not too much detergents. Some crossovers, like Rotella T 15W40 synthetic - although made for deisel trucks - work well in a motorcycle because of it not having a high amount of detergent. Basically, it's a preference thing as long as you know your not putting something inside your bike thats gonna screw it up.