Poorly xj 600

Hi everyone,
I bought myself a 92 xj600 Diversion yesterday from Ebay. Bad idea I know, but it was cheap and maybe I have now found out why!
It got me the 40 or so miles home and there seemed to be plenty of power there, but everytime I stopped at road junctions/traffic lights, it started to backfire. I put it down to it needing a good service.
When I got it home, the nightmare began!
I revved it up to around 6000 rpm in my yard and it blew clouds of black smoke out of the exhaust. My initial thoughts with the smoke being black, was that the mixture settings were miles out and this might be causing the backfiring as well. It blows black smoke out when the engine is hot or cold.
After googling it, I found out the mixture screw is set at the factory and cannot be adjusted. Has anybody any suggestions on what I can try, or is the engine completely worn out. (I always thought black smoke meant fuel mixture problems and if the engine was worn out, it was blue smoke!)
Next problem:
I tried to take the seat off, but the key I have will not operate the seat lock. Is there anyway to take the seat off without damaging the lock or the seat?
Next problem:
I noticed that the chain is really slack and tried adjusting it, which is normally a really easy job to do. However, when I get the tension set correctly and then sit on the bike, the chain is extremly tight. The chain seems to have been replaced recently so isnt worn out. The only thing I can think of, is that the rear shock is so worn, that it is compressing too much with the weight of me sitting on it, and then taking up all the tension on the chain and making it go tight.
The bike itself is in reasonable condition for the year, and I would love to get it running properly without too much expense. If not, its going to be totally stripped and all the parts sold off on Ebay which really seems a shame.
Any help or advice would be greatly appreciated.
Denis

 

I think black smoke is likely to be mixture or a choke stuck on. I can't help on the seat issue and reckon a manual is a must. The diversion carbs are different in construction to most xj carbs but most older xjs have a removable (Well sort of) plug which gives access to the mixture. UK bikes are not normally plugged.

I had an ebay bike last year and found various bodges/faults but they weren't too bad.

If there is damping when you bounce on the seat the shock should be ok. try setting the chain tension to account for you sitting on the bike.

 

Hi and thanks Markie.
The idea of a sticking choke had crossed my mind too, but I didnt want to remove the carbs and start stripping them down only to find out it was a worn out engine after all.
I actually got a Clymer manual with the bike, but it only covers the pre-diversion models. I am a true Haynes fan and am bidding on one on Ebay right now, but until then, I'm stuck.
I could live with the backfiring at tickover, but its very embarrasing when I'm sat at the traffic lights next to another bike and my poor Divi is popping and farting, sometimes very loudly : (
As for the seat lock, I got in touch with the guy who I bought the bike from, and he assures me, that the key he gave me, does operate the seat lock! Even more WD40 is needed I think!
I tried adjusting the chain with somebody sat on the bike, and it still rattles when riding it. Also, when parked up with no weight on the bike, the chain has almost 2 inches of play in it. I have been adjusting chains for the last 30 years or so, and have never had this much trouble.
Regards,
(A very stressed out) Denis

 

Hi Denis. I downloaded a haynes manual for a diversion in pdf format free by googling "xj600 free manual". I can probably email certain parts to you but the whole manual is 65 meg so a bit big.

I owned a pre diversion 600 which had different (More complicated) monoshock system so wonder if the nylon block that the chain runs over is worn/missing? It could be the damper - had to replace mine, not a cheap item.

Check my gallery for some of the horrible things previous owners do - mine had a pair of tights for an air filter!

My 600 came from ebay and the p.o. promised me it was fine to ride 60 miles home. It spluttered to a halt on the wettest day of the year after 3 miles (Fuel tap problems)!!

 

Hi Markie,
I already thought of that and the nearest I could find was a manual for the pre Diversion which I downloaded anyway, but its not much use as there are so many differences, esp the carbs! I'll keep looking for one!
The nylon block is still there and looks in good condition. I have actually just had another thought, what if the chain is not as new as I first thought and has really stretched? I have just checked again on the alighnment marks, and there is only 1 more alighnment mark left on the swinging arm. I suppose a new chain might not go amiss, but the black smoke, together with the popping and farting is my main concern at the moment. My wife refuses to risk spending anymore money on a bike that is only fit for scrap.
The guy who I bought the bike off couldnt have been more helpful, but after doing some research on his ebay history, I found out he had bought the divi himself off ebay 3 months ago. His excuse for selling the bike was that he had just bought himself a 600 Hornet. I know he has a hornet as he actually picked me up from the train station on it. Maybe hes just not that mechanically minded when it comes to bikes and had no idea where to start on fixing the divi's problems! As long as I know what I'm looking for, I can usually fix most things.
I have been lucky before when buying bikes as the 30+ bikes I have owned, have been reasonably maintained when I bought them. Cars are a different matter and I can relate to what you say about previous owners bodge ups. Bought one car years ago and the engine seized on the 3 mile drive home! No oil, no water and the sender units had been disconnected! :evil:

 

send me you email address via private message and ?I will send you the wiring diagram.
Mark

 

Splashed out on a Haynes manual today and it told me what I already knew. Its running too rich.
I replaced the air filter and the black sooty plugs and no difference.
I would like to try adjusting the mixture but the manual says it is factory set and cannot be adjusted and gives no info on it all all. I cannot even find the adjustment screw.
In the past, its been a case of screwing the adjuster in all the way and counting the turns. Unscrew it again and then start adjusting it a 1/4 of a turn at a time.
Is there only one mixture screw or is there 1 on each carb?

 

Hi Denis - I just checked my Haynes manual and either part 19 (Early bikes) or part 5 (After 1996) is the pilot screw. The early screw is to the rear of the carb and the later one to the front of the carb. The manual I have covers the xj600s and n models.

Check out the exploded view. 1 on each carb.

In a lot of earlier us spec xjs like the 550, the pilot air adjustment was blanked but the blanks can be (carefully) removed.

mark

 

There's one on each carb like Mark said, and each one is covered by a plug that must be drilled out. It takes a steady and careful hand to do so, because you risk drilling too far and damaging an already fragile screw underneath.

Let me grab my camera and I'll take a pic of where the screws are at -- it's up to you if you want to start drilling.

In the meantime, read up on Rick's carb cleaning write-up. There's a part in there that describes the drilling procedure.

 

Here's the little guy:

 

try turning the key left instead of right Or vise versa (The other way then the helmet lock). I had a similar problem with the seat until I found out that obvious but sneaky little thing.