WON'T START AFTER WET SETTING FLOATS AND DRY BENCH SYNC?

I've just wet set floats, and all seemed in spec. Dry bench synced to thickness of a paperclip across all four carbs.
Reinstalled carbs. Recharged battery. Tried to start, turned over and over....Nothing.
Turned petcock to 'pri'....nothing. Turned to reserve....nothing.
Took plugs out and smelled them....hardly any fuel smell.
Tried with choke on (circuit enrichment!)...still won't fire up.
Checked I've got a good spark....fine spark on #s 1 and 4 anyway.
Flattened battery now, so recharging it.
Why is the fuel not getting through to the plugs hardly.....any ideas PLEASE?
Regs.
D. Grantham

 

back off the idle a half turn, set the mixture screws 2 3/4 turns out
the enrichment is most effective with no throttle, a fat paper clip might be open too far for it the be effective

 

Ok Polock, I'll try that when battery recharged. (already tried turning idle up and down though) Do you mean the mixture screws that are between the carburettors 1 and 2, and 3 and 4 please? (or are they the sync screws?)
I am presuming I have resolved the stuck float issue, because there is no leak anymore. (just the opposite in fact - a drought!!??) - lol!

 

Those are the SYNCH screws, they adjust the relative positions of the throttle openings of each adjacent carb.

The MIXTURE screw is the straight-slot screw way up to, next to the choke plungers.

Make sure your fuel tank isn't empty. If you wet set the fuel levels, then obviously the float valves are working.

 

Doh, yes of course they are Len(?). Didn't think I'd have to adjust those from how they had been set by colortune (but that was obviously from different sync-base?) The fuel tank is 1/3 full. Will check it is flowing out of that though also.
When I wet set the fuel levels, used the 'tube attached to float bowl' method, and all four carbs were filling up with fuel to line I had drawn on outside of each float bowl to specified +/- 2-3mm (between 2 and 5mm below top of float bowl), whatever. The level lines were still there from when I last wet set.
Can I perform these tests, using temporary fuel supply, with the tank off to try and get the darn thing started?
Regs.

 

Just tried all advice given, and still not even a sniff of an explosion. (Using temp. fuel source while I do this, and putting finger over vacuum pipe that would normally connect from petcock to #3 cylinder) Backed off on idle knob, turned mixture screws off and then reset to 2 and 3/4 turns out, applied enrichment......and still NOTHING. The plugs are bone-dry almost, no smell of fuel on them. Do I have to take the carbs off and look at something again? OR - is there something I have missed perhaps, something basic....?.......WHY is the fuel not getting through to fire up the engine?

 

Is the fuel hose to the carbs running from the petcock or from a "temporary fuel source"?

If it is from a temporary fuel source, make sure the source is vented (so fuel can actually drain from it) and then open a bowl drain screw(s) to see if fuel is flowing into (and then out of) the bowls.

If the fuel source is the petcock/fuel tank, then put petcock on PR (prime) setting and see if fuel flows out of the petcock. If so, then hook fuel line to carbs, open bowl drain screw(s), and see if fuel is flowing into (and then out of) the bowls.

If fuel is not flowing out of the temp fuel source or the petcock/fuel tank while petcock is in PRIME position, then that is the issue that needs to be addressed.

If fuel IS flowing out of the fuel source, but no fuel is entering (and then draining out of) the fuel bowls, then there is either some type of clog in the fuel hose/fuel inlet T-fitting/fuel pipes, or, the fuel inlet valves have seized closed for some reason. Floats set incorrectly (doubtful, you said they were working prior).

 

Now carbs are back on machine, to do any adjustments (ie get at mixture screws and/or sync screws) I have removed tank and hooked up temp fuel source. Yes, it is vented, and fuel is flowing from it when turned to 'open'. Same with the petcock when in 'PRI' position, and no fuel flows when set to 'ON'. I shall attempt the test you advise, by putting tank back on, but I think I can only access #s 2, and 3 drain screws because (as you probably know), #s 1 and 4 screws face inward, and I cannot easily access them when carbs installed (unless extremely long shaft screwdriver with narrow blade?)......trying that now, and THANK YOU for your attention.....

 

Just tested, with petcock in 'Pri' position, drain screws #s 2, and 3, and fuel flowing from them, til I close them again....? (tried to start, just in case?! no luck)
Could the backfire I had, a week or so back caused some sort of clog in the fuel supply, or seized closed the fuel inlet valves, as you suggest, Chacal? I have had the carbs off since then, and done wetset, and bench sync. As the plugs seem to be getting little or no supply of fuel in the combustion chamber (not one 'explosion' in all my trying), and are bone dry, they logic suggests fuel is not accessing chamber from carbs?

 

It sounds like float bowls 1 and 4 have been swapped. You should have access to all of the drain screws.

That's probably not going to make a difference in your fuel supply problem. Just sayin'.

 

Ok thanks bmarkza. I could have been the culprit, when resetting float levels on those two chambers(?) Point taken, and will rectify when (as I probably will have to (!!), I remove the carbs again.
Just been looking at history of threads, for 'not starting', or 'hard to start', and clogged fuel enrichment wells are high in the charts for causes of this?
Regs.

 

Just tried the old trick of trickling a thimbleful of petrol down each spark plug hole, to see if that would spark it up......no chance, turns over and over and over.....nothing.
Suppose I'll have to take the carbs off and check everything is in spec again, and the fuel enrichment wells are in clean order.

 

Left it for a few hours, then tried again.......backed the idle screw right off, set to 'PRI', ....got a cough.....then it started....cut out......started it again...backed screw out again, then in......ran for five minutes......set to 'ON'.......continued running, lovely steady idle of 1050...those bicycle innertube manifold vacuum leak seals work a treat now I've reinstalled them.
Thanks for all your contributions....
Regs.

 

Glad you got it running......question for you though--

When you did your carb cleaning did you make sure to thoroughly clean the enrichment tube AND the enrichment well in the the bowl? At the bottom of the well is a small jet that can easily clog. If that jet is not very clean and clear, then the enrichment circuit can't get the fuel it needs (or can't get it fast enough, which may indicate why you were able to start up later after the wells had their chance to eventually fill up).

Now, another thought-- These bikes each have their own place that they like the enrichment lever to be. My 650 liked it all the way over to start, then back halfway, then off after 2 mi or so. My 700 likes it halfway over, then off after about half a minute. My 900 likes it all the way on, then halfway off after about half a minute, then off half a mile up the road.

I tell you that simply because you may find out that it simply "not the right amount of enriching yet"........



Dave Fox

 

Interesting, I m having the same issue. I can get it to start, but not hold an idle. I removed the emulsion tubes and cleaned them, along with everything else, but for some reason I am not able to keep the bike running. As it was stated, the bike will struggle to start, but it starts easily if I let the fuel sit for a few hours. As much as I hate to pull the carbs again, but if I gotta, I gotta.

 

Where do you have the mix screws set at. Might try backing them out 1/8th turn or so.

Gary H.

 

I've still got problems starting it, after it has sat for 24 hours or so. (I even got a perfect vac sync the other day, once running?!) Flattened the battery again last night, (and got TWO backfires!) but after I waited for it to recharge, started straight away, and after a couple of minutes of 'up and downing' with the rpms, it settled down to the right idle at op temperature, and I was able to turn off and it started up again no problem. Will try 'rocs' suggestion of turning mix screws out another 1/8 turn, combined with 'hogfiddles' (mine's 650 RJ SECA), enrichment 'all the way over', with petcock in 'ON' position (ie automatic vacuum?)
Going to try now, and be back with results
Still think I'm going to have to pull carbs, and re-dry sync, with starting point butterfly gaps almost closed....(?)
A couple of months ago, I used rebuild kit on petcock, and the drysync starting point had been set same as when the petcock had been defective(?) The petcock is obviously working as it should now, and may be affecting the start?
Regs.

 

Just tried it with idle knob almost all way out (ie barely engaging throttle), with enrichment circuit (choke) on full (ie all way to left), and in 'PRI', on petcock to start with, and it started second time! Built up high obviously, but gently tweaked choke out til idling @ 1300-1400, turned petcock back to 'ON', allowed to get up to temperature (@4-5 mins), and with an adjustment of the idle knob (in), and the throttle off, achieved a nice 1100 -1150 idle. (anything lower at idle and starts to drop too low - when running (in motion) you can drop it to 1050-1100.)
Didn't touch the mix screws - they are set at 2 and 3/4 turns out each at the moment. As I said in last thread, I have got a very decent vac sync, but still need to fine-tune with colortune, for best I can get.
Hope this helps?
Regs.

 

Sounds like you've got it. 2-3/4 turns on the mix is a good starting point. You should be able to tweak with the colortune without it dying.

Gary H.

 

I like to put the mixture screws at 2.5 turns out from soft-seated, and then I go just about 1/8th more. I RARELY have to adjust from that point.

 

Yes, I shall set the mixture screws to 2.5, hogfiddles - that's where I always used to have them - and adjust accordingly as necessary. The idle is a little high with set at 2.75, and although starts, have to start in 'PRI', with enrichment (choke) 3 quarters across, and then turn back to 'ON' when got running.
A bit of tweaking, get the best start point, then check vac sync ok, and then colortune.
Regs.

 

PS - Got a perforated front left (#2) down pipe header, half way down pipe, blowing when in motion. Gonna temp fix with bandage, but ob need to get another one, or full set if right price.
There are numerous for Maxim on web.....QUESTION: are Maxim and RJSECA downpipe headers for 650 interchangeable? (I know they are different OEM #s, but they look the same in photos?
Anybody confirm, yeh, or neh?
Regs.

 

They are not the same, bend angles are different, output flange diameters are different. We should have some good used ones available.......

 

They will fit if you use the 650 mufflers.... The 650 Seca collector is different at the front, plust the Seca has a full collector whereas the maxim just has simple 2-into-1 joints that are part of each muffler, along with a simple crossover pipe-----

Actually, other pipes/systems will fit, but it's a lot of mix-and-match to figure it out. I did a write up awhile back, I'll see if I can find it---

 

I think his question is about the HEADER PIPES (headpipes); the 650 Maxims don't use a traditional "collector box" like other models do.

The size (diameter) of the shrunken down end of the header pipes is different between the 650 Seca and 650 Maxim models.......so, even if the bend angles of the pipe were the same (and they're not), you could not use the Maxim headpipe going into the Seca collector box because of the size difference.....


XJ650 Maxim headpipe output gasket:
ID: 31.80mm
OD: 37.67mm

XJ650RJ Seca headpipe output gasket:
ID: 28.65mm
OD: 32.47mm

 

I know he was talking about the header pipes.....

I can't find my exhaust comparo write-ups, but if you have those measurements, then obviously they won't work. I know one of the experiments was with the with 750 Seca pipes on the 650rj, and even though numbers are different, they fit perfectly...... And I did a bunch of swapping around using various combinations of pipes and collector boxes.... And I mounted them on a couple bikes to verify.

I hope I don't have to do it all over again..... Lol

 

Yes, that would be a pain!

The XJ550 (all models), XJ650 Seca and Turbo models, and all 1981-83 North American (and their rest-of-the-world counterpart versions) XJ750 headpipes are the same SIZE down there at the collector input (the XJ650 Maxim crossover pipe stub pipe is the same size, too). But the bends are different, so even though the headpipes will physically swap/fit inside those various collector boxes, the distance and bend angles of the pipes themselves are different, and thus may cause a mis-alignment when actually trying to do such swaps on an actual engine installed in a particular bike (we tried doing this on a couple of different bikes --- can't remember which ---- and finally threw up our hands and said "no way this is worth the effort" since there are so many different permutations of what-might-fit-what, and decided that Yamaha had already figured it out, and if bike headpipe "A" is a different part number from bike headpipe "B", well, there sure was a good reason for that.......

You can do it again as a proof-of-concept (or, if you get really bored someday and have nothing else to do!), but, I think you'll also end up have a Aw-Hell moment, too, and reach the same conclusion.

 

if you don't have a colortune, when it's good and warmed up, adjust the mixture screws for the highest idle, then 1/8 turn more, use the idle knob to keep the rpm's at 1200, that's the old school way

 

Thanks for all your feedback. From what hogfiddles says, can I take it that the 750 Seca headers are the only ones interchangeable with the RJ650s then?

 

Don't take it that way...... I experimented with mixing/matching things. That was it. I did a write up of what had fit and with what combination, but I can't find that anymore.

Part of the issue is the angles on the pipes, another part is the angles of the receivers.... I swapped pipes and receivers, etc..... And what it seemed to come down to was the best fit would usually be a matched collector/pipe set, though some other combos did work. Examples:

I did mount a 750 Seca collector and pipe set in the 650rj. I also fit a 750 maxim collector on w/ Seca pipes, and vice versa..... The biggest difference was that on one configuration the center two pipes stood out from the outside two. The still mounted fine, just looked different. Unfortunately I don't remember which combo was which .....

So until I can play around with them again and re-write it , go with what Len says.

Dave

 

Imo make life easier. When/if the stock set up becomes obsolete and there are no straight swaps from other bikes go with a good aftermarket set up and re-jet as necessary.

Gary H.

 

I don't like aftermarket set ups.....