V45 Sabre engine rattle

I have an 83 V45 Sabre that has developed a very odd problem. The engine rattles/rumbles pretty bad at low RPM's, it seems to be coming from the rear of the engine. It is NOT the cam tension rattle as it goes away completely when you pull in the clutch. The bike has been sitting for 2 years. When it was parked, it did not have this problem. I put in a new battery, rebuilt the carbs, then fired it up only to hear this rattle. It runs perfectly and I am stumped. One other thing, I replaced the clutch slave cylinder as well with a new one from Honda. It has 11K miles on it and I am not tearing into the engine. If that is required, look for it on e-bay as a parts bike. It is in near mint condition, never seen rain and lives in my climate controlled basement. Also, it shifts fine and the clutch works fine, it just has this very bad sounding rattle/rumble engine noise. Any help is appreciated and thanks in advance.

Actually, I did not change the oil(brand new oil when it was tucked away), but I did pull all plugs, then crank the engine fast(with no compression) to get oil through the engine. Plus, the noise is definitely coming from the bottom end, sounds like somewhere in the tranny. I used a stick to my ear and isolated it that far. But I don't want to run it too much in case there is damage being done. Keep in mind, if I pull in the clutch, even in neutral, the noise completely disappears. Thanks for the reply.

The clutch cover on the right side of the bike will be tough to remove. The beast is after all 28 years old. But even if I had the cover off, I have no clue what to look for. I have the shop manual from Honda. I will check to see if I can even get the gasket from Honda. If not, she goes on e-bay as a parts bike. I never rode the darn thing anyway. What do you think about just taking the old gal for a ride? Maybe that would lube/loosen up what is dried out and rattling? I have not done that yet.

This bike has a very nice center stand that lifts the rear wheel off the ground and level. I have tried putting it in gear and letting the wheel spin for a bit, but just a bit, did not want to hurt anything. One other note to add. Not sure if you are familiar with these bikes, but they were poorly designed in the way they provided oil to the top end(cams etc). There are aftermarket kits you can get to provide higher pressure to the top end oil lines, and also filtered(stock is low pressure and not filtered from the tranny). I have had one of these kits on it since about 7K miles. Now if you are not familiar with these kits, you wont likely know what I am talking about but I did have to tighten down the oil bolt on the engine block that feeds the oil to the heads(slight leak for some reason). This bolt also blocks the original oil passage. I am wondering if tightening this down made it touch something in the tranny? Cant really loosen it to test or I will have oil everywhere. Anyone know what is beneath this oil passage?

My thoughts exactly, but I will not be able to get to it until next weekend. I am going to call a local shop that works on older bikes and see what they think. More later ...

Well, I was able to pull the bolt that holds the 2 banjo connectors on the engine block for oil to the heads. I was looking for marks on the end of the bolt to see if there was anything hitting it after I tightened it further. End of bolt was clean as a whistle, no indication it was making contact with anything. Next, just for curiosity, I drained the oil to see if there were any metal filings which would indicate a VERY serious problem. Oil was like brand new and NO filings at all. At this point, I think this baby just need a good romp on the street. I am thinking one of the clutch plates is caddywompus from sitting so long? Raining here today and likely till the weekend so I will update later this weekend. Thanks for your replies.

I will take it easy! What I really should do is go out and buy me a new hog. I have always wanted one, and I can assure you, if I had a hog, I would ride. All my buddies have hog's and they wont let a rice burner tag along.

Well, I took the beast for a short spin today. Engine rattle still persists. I am going to see if the clutch cover gasket is still available from Honda. If so, I will remove the cover to see if there is anything obvious. If it is not an easy fix, she goes to the scrap bin for parts. Kind of sad, the bike is in mint condition. Someone will get a REAL nice parts bike. I just cant figure out what would cause this from simply sitting for a couple of years.

How about this?

I worked as a service writer in a transmission shop for several years. I learned what sounds go with that problem.

Grinding sound (or rattling) with the clutch engaged that disappears when the clutch is disengaged is a mainshaft (input shaft) bearing problem, usually on the input side vs the other end. I'd call it the input bearing.

In neutral, with the clutch engaged, the main shaft (input shaft) is spinning and a bad bearing makes noise. Disengage the clutch and the input shaft spins to a stop and the noise stops.

Of course, you have to remove the engine and disassemble the crankcases to get to it (them).

The good news is you can see if your cam oiling system did any good and look for potential tranny problems while you are at it. That is good news isn't it? *lol*

I've had Japanese bikes and cars most of my life and never been able to break a transmission in one. Never use the clutch for up-shifts under power on the bikes and had a Honda CRX-SI that I used to take up into the Santa Cruz mountians and drive like a race car, lot's of second gear corners powering near red line, heel toe shifting, using all it could give, almost daring it to break. I did have the input-shaft bearing get noisy on that one, so I replaced the clutch while I was at it, which it really didn't need. I could make the 3-4 and 4-3 shift on that car without the clutch without too much protest, although that's probably what beat up the the first bearing in the transmission. Still, I've never had a more fun to drive car.

Anyway. Noise goes away when you pull the clutch lever in, think about what stops. It's the input side of the transmission, and in neutral the only thing that can make a noise is a bearing.

To be clear, it makes the noise anytime the clutch is engaged right? Neutral or rolling.

Well, it has been a while since I updated this post. I will try not to be too verbose. This whole mess started with oil leaking from the clutch slave cylinder rod oil seal. I "assumed" I could replace the seal from the outside and in the process, buggered up the seal(but I did get it out) and also buggered up the casting holding the seal. I noticed this leak and the engine rattle at the same time. The only way to replace the seal was from the inside which meant I had to get the casting off the engine. To do this, I had to remove the real wheel and the drive shaft. But, the casting would not come off as the shift linkage lever was preventing it from pulling out as the frame was in the way. So, I had to pull the shift linkage arm out, which meant removing the clutch(right side cover) and then sliding the shift linkage shaft out the right side of the engine. In this process, I had to remove all the clutch plates, oil pump chain and other stuff. But I did get the casting off the left side of the engine, replaced the seal, put the whole mess back together and fired up the beast. Lo and behold, the rattle is now gone. I have no idea why, but it is gone. I should mention that the left side casting that I buggered up was replaced with a very nice one I found on E-bay. So at this point, I am now back to a poorly running Sabre due to the carbs needing some adjustment. But I am taking it into a local shop to have that done. I sure wish I knew what actually fixed the rattle but I have no clue. Thanks to everyone for taking the time to offer help and suggestions.