New XJ650 Turbo Owner doing a rebuild

Hi All - I recently bought a 1983 XJ650 Turbo which came as a rolling chassis and a number of boxes. I have been trying to ask for some advice on carbs and float heights but the forum won't let me post as it thinks my posting is spam! Any suggestions on why and/or carb float height settings on the turbo would be welcome.

 

Not sure when it last ran so I stripped it down to the frame and over the last month or so have rebuilt it. Looks great now however I am having issues with the carbs which seems likes a common problem. I have thoroughly cleaned the carbs which were all gummed up but have not as yet managed to get hold of rebuild kits. I ultrasonically cleaned all jets and needle valves to the point where they were clear. First time trying to start the bike and of course it badly flooded so I have pulled the carbs again. Number 2 cylinder seemed to be the culprit as fuel came out of the carb as they were being removed and there seemed to be some in the plenum also.

So I thought I would check the float heights - not so easy as the workshop manual specifies in one place 17.5mm and in another 21.5 but in neither case does it actually show where the measurement is taken from. Number 2 seemed to have a larger float height but to me a larger float height will close the valve earlier not later. So any suggestions on how to check float heights and what measurements for the Turbo would be welcome. I have seen the suggestion to check fuel height but I can't see how this would be done as there is no fuel take off on the bottom of the float bowl, just an untapped hole where the fuel comes out of when you loosen the drain screw - do I need special drain screws?

I did also find that a needle valve seemed to be sticking slightly so I stripped and cleaned it again and it seems better. With an external fuel tank connected to the carb inlet I checked for leaks and none were found - but the carbs should be pressurised when running? So I tried blowing 10 PSI air into the fuel pipe and fuel bubbled out of the 2 holes on the inlet mouths - not sure if this is an issue though.

I really would welcome any suggestions as I'd love to get the bike running. I have some rebuild kits on order which contain gaskets and new needle valves/seats but without an idea as to what the problem might be I'm not sure what effect these would have as the float bowls weren't leaking anyway!

 

Setting the fuel levels

The specified fuel level is the same for your carbs.

@chacal stocks parts for the Turbo.

A few more posts and the spam /warning blocking will go away.

 

Congrats on your turbo Cmd..., I'm trying to figure out where you are in "the process". You mentioned that you ultrasonically cleaned the jets/needles but did you pull the carb bank and run it in the bath as well? There are two ways of getting your bike running....the Q&D or more in depth so that each cyl runs perfectly and in sync with the others. It sounds like you've taken the 2nd route and are close to completion. Let me know if you need the turbo manual....free of course.

Typically, if everything has lived a while in the ultrasonic, I'll re-brass each carb, setting to identical specs, then will set the carbs so the slides are all dead-equal and showing a skotch of light....then mount them, start the bike letting it warm up completely...then hooking up the carb stiks. I leave the tank off during this with any bike, using a radiator overflow tank as a small, portable fuel supply while hanging on the left grip. You did check the valve clearances, right? Makes a big deal when tuning.

Most of the turbo guys hang out here and in the Turbo forum....Chacal won't mind that I post this and he's a sharp, knowledgeable guy and a pleasure to deal with.

https://www.tapatalk.com/groups/tmioa22687/yamaha-seca-650-turbo-f10/

WTTC!


jeff

 

go to the page I've referenced below. This is a trick I came up with to mount clear battery overflow tubing to the Mikuni.

https://www.xjbikes.com/forums/threads/fz600-resto-the-hotrod-xj.99949/page-2

 

Thanks all - I stripped the carbs again and I think it was a sticking float valve in #2. Re-installed and to my amazement it started and ran. Sounds OK with no exhaust blowing but couldn't run for long as I was on an external fuel tap and my coke bottle filled up pretty quickly from the overflow! Waiting for a fuel tap repair kit to come as it leaks from the tap to tank seal. Also need to drain the oil again and change filter as no doubt quite a bit of fuel made it into the oil the first time around.

Shims were done - surprised how easy it was to do although I had 4 inlet and 2 exhaust out of spec. Only needed a few shims though my moving things around. First time doing shims so a pleasant surprise it was so straight forward. I'll take a look at the links to see how best to set float / fuel heights as I have skipped that step so far. The carbs were setup statically as best I could but I have vacuum gauges for when it's running properly. Onto the next job - see next post!

 

Continuing with the rebuild and everything is back together save for the bodywork which I am planning on getting painted once the decals from the US arrive. However now I have hit a snag with the rear wheel. I didn't get the bike in one piece so I have found a few minor parts have been missing and also the previous owner looked like he had done a partial rebuild of some bits.

I re-installed the rear wheel including the spacer which goes by the brake drum and the washer which goes under the nut and tightened it up - the rear wheel locked up solid. Loosened it up a little and although the wheel turns you can hear and feel it binding. Initially I thought it was the new brake shoes I had fitted so i stripped it again, removed the shoes and put it back together - exactly the same.

I then checked the wheel bearings and realised they were new - however the bearing on the drum side was flush with the housing but the bearings on the drive side were in the wheel by 1-2 mm. On closer inspection I could see that the bolts attaching the flange to the wheel were bottoming on the driveshaft housing. My thoughts at this time is that the bearings are sat too far into the wheel allowing the wheel to be pulled into the housing too far and causing the problem. Saying that I may be missing something but even looking at the parts diagram I'm not clear what it could be.

 

Try to keep all posts about a specific bike in one thread, easier to follow. That being said, if the PO changed the rear wheel bearings it's possible he omitted the spacer that goes in between them which would cause the condition you describe on the one bearing being installed too far inboard.

 

ok - I assumed it would confuse matters if I asked a different question on the old thread... The long 'tube' spacer is there between the 2 sets of bearings as is the thin 'shim' which sits on the inside of the brake drum bearing. Tried to upload a picture of the hub side but I think I need to host them and link to the picture. I'll have a read up about that...

 

Merged to maintain clarity.

 

One of the common causes for that trouble is not toghtening the fasteners in the correct order.
The axle nut gets brought up to torque before the pinch bolt is done up.
Reversing that order causes the swingarm to be drawn in when the axle nut is tightened, which can cause the whole assembly to bind.
There are other issues that can cause it all to bind up, one of which is not having the correct spacers.

 

I have spent the last few months restoring a 1983 XJ650 Turbo which I got as a rolling chassis and a huge box of bits. It's been stripped to the frame and completely rebuilt including a full strip down of the carbs, turbo, forks, brakes and pretty much everything else. Today it finally passed it's M.O.T test meaning it is legal on UK roads. It is not without issues though which I was hoping for some help with.

First issue is the clutch. When i pull the clutch in there is a distinct rattle/ticking noise - quite loud - coming from the clutch area. I have replaced the 'release bearing' but that has made no difference. Just stripped the clutch out totally and swapped out the basket as I had a spare - no difference. Only thing I did notice was the oil pump chain was very loose but there was no obvious adjustment so I guess it's just stretched.

Second issue is the way the bike runs. The carbs have been rebuilt with new 'O' rings, floats and jets from bdesign and once warmed up and on boost it seems to go well. However it just won't idle. If I adjust the idle speed so that it will idle it hangs on to the revs when you blip the throttle - it seems to be cutting out on at least one cylinder at idle speed. I went for a quick ride and when I got back checked the temperature of the downpipes. #1 and #4 were around 100C whereas #2 and #3 were nearer 130C. If anything #1 was probably nearer 90C but it's difficult to get an exact reading. I have balanced the carbs ad they should be spot on. It's probably mixture I would guess but which are correct and which need adjusting? I suspect and issue with #1 cylinder as when I start from cold it seems to take a while to join in but I really don't want top pull the carbs yet again!

Last issue for now are the front forks - these have had new seals and oil but just don't feel 'right' . They chatter over uneven surfaces and don;'t seem to bounce back when you push down on them. They are much better since I re-tightened the front wheel spindle once the hole in the fork legs had been cleaned of powder coat. I guess that was preventing the wheel spindle from tightening up correctly and was causing the forks to twist a little.

 

did you replace the Cylinder Bearing and related parts? part 33 in this drawing

https://www.partzilla.com/catalog/yamaha/motorcycle/1982/xj650lj/clutch

 

I haven't replaced the bearing no - just the release bearing and now the basket. I would assume that the cylinder bearing would be noisy all of the time if there was a problem with it?

 

when you pull in the clutch you take the pressure off of the discs and plates and off of the basket.
I would revisit the clutch work make sure your bolts are torqued properly

do agree with you about the oil pump chain

 

Post
Rattling Noise On Start Up Yamaha XJ 900f

another thread
XJ Maxim 700 X '86 USA (49-state version) Gearbox Rattling
​

Post
Tried everything need help

 

I have posted a few times about idle issues I have been having with my XJ650 Turbo after a complete rebuild. The carbs have been completely rebuilt and then stripped manytimes again to try and sort this issue but so far no luck.

Essentially the bike runs great above idle, comes on to boost great and goes well when boosting but a little sluggish below 5K which seems normal. When I let the bike idle the revs drop to about 900rpm and will normally stall after a few seconds. If I wind the idle up on the screw, the bike idles around 1100 but blipping the throttle causes the revs to hang at about 2000 and then it drops back down after a few seconds which is disconcerting when you are riding. This suggests to me that the idle screw is artificially raising the idle to compensate for something else.

The last time I stripped the carbs off I took all of the pilot jets out and checked they were clear - they were. I then sprayed carb cleaner into the pilot hole and blew it through with compressed air - it came out of a small hole in the throat of the carb suggesting the pilot circuit is clear. re-assembled and exactly the same. Mixture screws have been set at 2 1/2 to 3/12 turns out but no obvious difference. Fuel levels are spot on and I have set the valve clearances and carb balance and have a yics eliminator installed. I also swapped a coil with another but none of these changes seems to make a difference.

I have just read another post which suggests that battery voltage can affect idle - is this the case and are there any non-carb items I can look at as I really think the carbs are spotless inside now!

 

I merged all of your threads so I could look back and see what's been done so far.

I see several mentions of cleaning the carbs, but no mention of replacing any of the rubber parts on the carbs.
Your sumptoms could be caused by an improper carb synchronization, or a vacuum leak.

Were the throttle shaft seals and idle mixture screw o-rings replaced with new?

Have you performed a running carb synch?


I'm adding this for the future, but you can check now if you'd like. You have installed a YICS emiminator (unnecessary IMO, but no harm to having it). It is uncommon, but quite possible, to have a vacuum leak at a YICS manifold plug. One cause is reusing the crush washers without annealing them first. The other is a crack in the casting, which can happen if the plug was difficult to remove, or overtightened.

 

Thanks for the suggestions. I haven’t replaced the carb rubbers but I have tested to see if they are sealed by spraying carb cleaner onto them while the engine is running with no effect suggesting that there isn’t an air leak there. I have replaced the idle screw o rings but I haven’t replaced the throttle shaft seals. I did try on a spare carb to Dremel the screws and then remove them and got one out and the other all chewed up so decided I didn’t want to do that to my built carb set. Again though I have sprayed carb cleaner on the shafts to see if the idle increased with no effect. I know that these can give problems when you rev it even if ok at idle but my problems are just at idle. Same with the yics screws, no obvious vacuum leaks there... carbs were balanced when running but I had to wind the idle up a little so it would run long enough to get the balance right. #1 seems to react a little quicker than the rest but at idle they are correct.

 

Did you check the fuel levels in the float bowls? A slightly low fuel level can cause symptoms that mimic a vacuum leak.
Setting the fuel levels

 

I did check the fuel levels and they were all within spec - assuming I read the instructions correctly which were 3mm BELOW the carburettor joint line which I read as the bottom of the top of the carb where it joins the float bowl if you know what I mean. Next time I take the carbs off I will re-check but the fuel levels were pretty easy to check with the carbs off as I found a rubber adaptor which fit into the float drain hole.