Newbie with a vibration issue?

[onerider]

Hello everyone, I am new to the motorcycling world and recently picked up my first bike a 1980 XS400!!! The motorcycle bug first bit me when my extremely nice cousin let me ride (after a bit of begging of course) his brand new yamaha yz125 dirt bike, right away I knew this was a sport for me. So after scouring through tons of classifieds I came across this beauty and for a whopping $100 dollars I took it home Then over the next few weeks I worked on getting it running. After multiple thread surfing sessions and carb cleanings she breathed her first breath of life in over 15 years! Since then I have given her a nice tuneup (valve adjustment, oil change, fuel filter, new chain, tires, and brake shoes) and it has really been a blast riding in this nice summer weather. Now the bad news, recently I noticed that it has a pretty bad vibration problem like foot/hand numbing and mirror blurring bad. Now it may have had it all along but I only noticed it recently. It starts at around 4k rpm and just gets worse the more the needle climbs. I tried to locate the source of the vibrations by cutting off the engine and pulling in the clutch at highway speeds (when most prevalent) and the ride is glass smooth so it must be from the engine. I checked the engine mounts and the rubber mounts seem to be good with the right orientation (I believe drewpy once had a problem with that) and tight. I then proceeded to check any gears that I could easily get to for play. I checked the alternator by wriggling my finger through the timing hole and then checked the clutch basket gear through the oil dipstick hole and to my surprise I noticed it does indeed have some play (around 2-3mm). So I guess my question is that normal??? and what else if not that can be the source of this vibration. Thanks in advance.

PS: I know how much you guys like pics but my camera has been giving me a hard time about working recently

 

[Scorpio1963]

Could it be your exhaust system is lose cause I had a vibration issue also which was caused by the fact it wasnt securely mounted to the frame.
It also could be that the tires are out of balance or are old and have a broken belt.
So question would how old are your tyres?
Is there play or excess loosness in the chain?
All of these will cause vibration issues.

 

[phate]

I agree with Scorpio check your exhaust and wheel alignment as that can also cause a vibration.

 

[onerider]

Thanks for the replies good idea with the exhaust because I remember hearing some rattling coming from the exhaust but i always assumed it was a loose baffle. could a loose baffle cause such bad vibrations? I will give it a better look later tonight. As for the tires and chain they are brand new and I checked the chain tension and its right at manual spec (3/4 in). Like I said I cutout the engine and pulled in the clutch during the vibrations and the ride immediatly became smooth as glass so I am really pinning it to the engine or engine component (ie exhaust) problem.

 

[16VGTIDave]

Swingarm bushings/bearings can cause a vibration if they are sloppy.

 

[Drewcifer]

What is the slack and age of your chain?

 

[onerider]

Thanks for the replies as for the bushings they looked fine when I took out the swingarm axle (to grease) and as I said before the chain is brand new with the tension set to 3/4 in as per manual specs. Besides aren't these things that I would detect in the highway engine cut off/clutch pull test?

 

[willem]

yea wouldn't make sense for the vibration to stop when you pull the clutch if it were caused by the swingarm bearing or chain. Definitely look at engine-related parts

 

[Lou Ranger]

I won't likely have a solution, but am curious to narrow down the problem.
From my reading of your first post, you are linking the vibration with a given rpm range - NOT with a particular cruising speed.

So, does the problem occur at 4,000 + in all gears or just in one? If it occurs in all, then I would guess that the problem is with something out of balance in the engine (here's where I am of no further use, since I can't even guess what).

If, on the other hand, it occurs only in one gear, then I would guess it is something awry in the transmission (here again, I am of no further use, since I can't guess what).
Looking forward to you next report ...

 

[HoughMade]

My first question is- have you synchronized the carbs?

Also, "numbing and blurring" don't necessarily tell me there's a problem. These things vibrate over 4,000 rpm. Maybe it's more than usual, maybe not. Have you ridden other old parallel twins for comparison?

Does it vibrate while still? Could you do a video to show it?

Have you looked at the engine mounts? Are they tight?

Rattling and vibration are not the same thing. Vibration may cause rattling, but usually rattling will not cause vibration. I would find it hard to believe that anything but a spinning part of the engine or trans could cause a significant vibration. Is the clutch in good condition?

 

[willem]

I agree with Lou, that it could be those things. But vibrations are sometimes not very straightforward, because they can be caused by interference and your bikes 'own' frequency. Imagine having a long plastic pipe in your hands, if you move it up and down at certain speeds it will swing out more than at other speeds. Same thing happens with your bike. If there is something loose on your bike, which could be anything from your mirrors to your tail light or exhausts (but likely something a little heavy), it could create a interference in your bikes vibration. This would make your bike vibrate at certain rpms, independent of which gear you are in.

in short, it may still be something not directly related to your engine. But what it is, nobody knows... only way to find out is to go through your bike front to back and check anything that is out of the ordinary. Check bearings, shocks, mounting bolts etc etc until you find it. good luck

 

[Lou Ranger]

Checking everything on the bike might be what you eventually have to do, however, I still recommend doing it using a differential diagnostic procedure.

i.d the most likely thing and check that first - as opposed to checking unlikely stuff first because it is the easiest. If it only vibrates in top gear at 4,000 rpm, check the transmission first. If it does it in all gears, take the tranny apart last, not first.

 

[16VGTIDave]

I'm in agreement with Lou. If the vibration is present in all gears at 4000 RPM and above, the problem is engine related.

I just discovered that the vibration in my Maxim, a buzzing felt in the bars and foot pegs above 6000 RPM, was actually caused by the ignition (TCI) module failing. Since I replaced the TCI module last night, the bike starts easier, pulls stronger, and is much smoother. It even sounds different.

I've been chasing my tail with carb jetting and tuning, chain tension, wheel / sprocket alignment, etc. I should have done a better job diagnosing the problem rather than spending dozens of hours making changes...

 

[onerider]

It seems that I was a bit vague in my description. The vibrations occur just revving it in neutral and in the rest of the gears (at all rpms past 4k) but I tend to reference the highway a lot because I am constantly maintaining RPMs above 4k. I have never ridden a similar parallel twin but not being able to ride on the higher longer then 10-15 minutes (because of the pins and needles pain the vibrations cause) kind of seems ridiculous by any standards. I have been messing around with everything trying to fix this problem including, carb sync (with homemade manometer), valve adjustment, tightening every bolt I can get a wrench on (especially the engine mounts) as I really am nervous about major engine work. I wouldn't even know what was wrong if I took the engine apart. That's an interesting point about the TCI box going bad is there any other way to test it without ohm-ing it out (it was well within the manual specs on that)? Also what about that clutch basket large gear having some play (in my first post)? Is that Normal? I really don't know what else to test.

 

[onerider]

Bump!
Any more advice? What about the play in the clutch basket large gear?

 

[arfstrom]

Give us a chance to digest this one. I like to make sure simple things are taken care of first. so Chain? how lose is it? Is the back tire on squarely? Since I have an older bike I can't say as the clutch basket, Wouldn't hurt to reset the clutch adjustment. We covered that in detail on a thread with words neutral, and 5 gear as key words. Once you taken care of the basics, then it comes down to the engine? who was the last person in there? PO or you? Does the electric start sound normal? could the kick start though out gear be getting caught on internally? Oil? are you using appropiate JASC MA oil? Ohhh you bike has a nifty oil check on top of the engine. I think its in the manual. I think it just lets you know that the oil pressure is getting to the top of the head. Its in the manual, that would rule out fuel pump? Do you have a magnet on a oil drain bolt? Are you willing to pull out the Oil sump screen to see if there are any bits in it? Replace the filter? in the last 4,000 miles? Thats most of the nity gritty worry wort stuff I can think of. Perhaps wheel bearings? Have you examine the front/rear bearings, greased up the axel bolt, (thats been on my mind) Check out the first chapter in the manual (which ever one talks about the periodic maintenance schedule.) Check the different seals on the guts, Clutch rod seal, output od seal, kick start seal, any other weird oil leaks. Look specifically at the Head gasket seal, if you have a power washer, sometimes bugs get in to the middle space between the heads, if you blow them out, I don't see how that would help, but make the engine release heat easier, I can see how we would miss that. Exhaust not working right?

I don't know if any of that would help. its a step, I guess

PS Willem back!!! Welcome back, How was your trip?

 

[Lou Ranger]

If it makes the same vibration @ +4k on the stand in neutral as it does on the highway, then you can rule out anything to do with wheels, suspension, drive-line or tranny. It has to be in the engine.

Have you checked the timing? I recall reading on here that one of our members had a faulty adjustment on the timing chain tensioner which allowed the chain to jump a tooth or 2 on one of the sprockets. Wouldn't it be great if it was something that "simple".

Failing that, looking for evidence of internal damage in the oil, oil filter and oil screen sounds like a really good diagnostic procedure.
If you haven't already changed and disposed of old oil, leave it out in the sun to warm up, then pour it through a screen lined with a "Bounty" brand paper towel. Any small detritus will be held there for examination once all the oil drips through.

 

[onerider]

Interesting news everyone!
After taking some of lou's advice I went out and bought a timing light from HF (with advanced timing control). I started on the left side and at idle its perfectly at the LF line but then when I rev between 2k-3k I have to advance the timing to about 52 degrees (an extra 13 degrees over the manual spec) to get it to line up on the LF mark. I then proceeded to the right side and discovered that THERE IS NO RF mark. This confused me greatly so I took a wrench and slowly turned the alternator and sure enough there was no RF mark on the alternator at all. I continued trying to gauge it off the RT mark (I know this is not going to be accurate but what am I supposed to do) and noticed its way off from the RT mark about 22 degrees at idle and way more when revved. What do you guys think?

 

[Lou Ranger]

I can visualize a miniature bike chain jumping a cog or two.
What you have just written above is "all Greek" to this non-expert. I just hope it will reveal the problem and that one of the Greek speakers on here will be able to guide you to the fix.

Failing that, how come you only took some of my advice?
What if the parts you didn't take turn out to be the ones to reveal the problem?

 

[Scorpio1963]

I agree with ya Lou I have no idea what hes talking about.I wasnt even completely sure if you can adjust timing on the bikes with electronic ignition but apparently you can.So far I havent had any need to mess with the timing my bike is running good right now knock on wood LOL.