1977 Yamaha XS750D

Bike fired up last night, sounded good with a real easy smooth idle.

The T's that connect the center carb to the right and left leaked fuel though. So I ordered them up (really really not cheap) Also ordered up the butterfly shaft seals, might as well replace them if I'm going to separate the carbs right.

Bike only started with the choke pulled out. Is that typical? It's not cold here in Southern CA. or do I just need to work on my jetting when I get it back together.

Thanks

these bikes ALWAYS need choke on a cold start, regardless of outside temp. If mine has sat longer than say 2hrs I need choke to fire up. few mins on choke then switch it off usually does the trick.

focusinprogress said:

these bikes ALWAYS need choke on a cold start, regardless of outside temp. If mine has sat longer than say 2hrs I need choke to fire up. few mins on choke then switch it off usually does the trick.

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Interesting. The XS850 I finished earlier this year didn't require any choke. Wouldn't run at all with the choke pulled actually.

clay69camaro said:

Well just been wiring lately. The new rear-set mounts are on hold for the moment, sort of prototyping, sort of...


Almost completely finished with the wiring though. I'm using these waterproof Deutsch connectors, they are pretty bad ass.

I'll throw the exhaust back on tomorrow and see if I can fire it up. If i can find the throttle cable that is.

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Love the teaser! Can't wait to see it. Where did you order your connectors from? I'm trying to figure out what to use to modify the wiring harness on my 850 cafe build.

hbc said:

Love the teaser! Can't wait to see it. Where did you order your connectors from? I'm trying to figure out what to use to modify the wiring harness on my 850 cafe build.

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www.cycleterminal.com/

I'll try and get you the quote for the header today.


Thanks focuinprogress, as long as it's not abnormal.

hbc said:

Interesting. The XS850 I finished earlier this year didn't require any choke. Wouldn't run at all with the choke pulled actually.

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850's run hitachi carbs which are an entirely different animal. the Mikuni's on the 750's need choke religiously, esp with the airbox.

focusinprogress said:

850's run hitachi carbs which are an entirely different animal. the Mikuni's on the 750's need choke religiously, esp with the airbox.

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The 850 I build had the Mikuni's, as does the one I'm building for myself right now. But I had POD's on it, so maybe that made a difference.

clay69camaro said:

www.cycleterminal.com/

I'll try and get you the quote for the header today.

Thanks focuinprogress, as long as it's not abnormal.

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I'm going to try going 3-3 with my exhaust so that I don't have to worry about welding the headers.

3 into 3 sounds good. I have to customize the one currently on my bike. I want it to hug the frame a bit more and it's got a fat crack in one of the pipes.

Shake down ride also revealed the newtronic ignition has a major problem with it. The switching unit (ignition box) is faulty. Bike will run for about 5-10 minutes then the ignition fully stops firing. So back to points till I can get this crap all figured out.

I fitted a Newtronic ignition to my XS750 project earlier this year, and had the same problem. The unit fitted well enough, and started first time, ran nicely for 10 minutes then cut out. Sent it back, and fitted the new unit, this time it ran for 20 minutes. The third unit was ok. Apparently the insulation on the pick-up back plate was faulty.

semmins said:

I fitted a Newtronic ignition to my XS750 project earlier this year, and had the same problem. The unit fitted well enough, and started first time, ran nicely for 10 minutes then cut out. Sent it back, and fitted the new unit, this time it ran for 20 minutes. The third unit was ok. Apparently the insulation on the pick-up back plate was faulty.

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Very interesting! Were they difficult to get ahold of for you?

Glad I still have my points. If all else fails I also have the '78+ electronic pick up plate, advance, and ignition box.

Not difficult to get hold of. I bought the unit from Yambits in the UK, but contacted Newtronic directly when I started having problems. Although it took a while things were sorted eventually. I'm not sure if I'd buy another though.
Hope you manage to sort yours okay.

Pity about the newtronic system. It seems I hear more failures of them then how well they run. But the bad always out weights the good.

On the other hand have you looked to see if a Dyna system will work for your bike?

Brodie said:

Pity about the newtronic system. It seems I hear more failures of them then how well they run. But the bad always out weights the good.

On the other hand have you looked to see if a Dyna system will work for your bike?

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No I haven't. If it all falls through though I'm just going to use the later model XS750 electronic ignition.

lets see the whole thing already!! btw I'm interested to know how that danmoto gauge is holding up

mAd mOrdigan said:

lets see the whole thing already!! btw I'm interested to know how that danmoto gauge is holding up

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Can't show the whole thing yet.

No seat upholstery, gauge not mounted, exhaust not fixed and re wrapped. Sill fighting the ignition issue so the bike kinda just sits in the garage waiting to get a solution from Newtronic.

I need to make a temporary gauge mount and get it back on, the tach will be useful for setting points timing, and getting the carbs sync'd.

Popping, kind of like a backfire out of the carbs. Timing is too far advanced? I think. These are later model cams of off like a '79 F or something like that, I don't remember hopefully I have that written down somewhere. They were also sent to Delta cams for a regrind for a little bit more lift, I wonder if that's keeping the intake valve open for longer. Hopefully I can rotate the timing plate enough to get everything happy. Otherwise I'm pulling the cam cover off and checking to make sure the cams are not off by a tooth or anything like that.

I don't think there's enough info, or it's really hard to find, for performance upgrades on these bikes.

Are you on the Yamaha triples forum? Tons of really smart guys over there, a lot of them have done major performance upgrades.

http://www.yamaha-triples.org/category-view.asp

yeah I'm on there, been searching like crazy. haven't found a real good answer.

Pulled off the cam cover and set the engine to TDC and the cam marks line up just right.

Maybe it's too rich at idle and I'm getting a bit of fuel lit off from the dead spark.

Wouldn't hurt to start a thread over there if you can't find your answer. Dudes over there are pretty open to new threads and helping you find what you need.

yeah I've got one going over there. No responses, that site doesn't really have that much traffic.

I think I might have figured it out on my own anyway. I treated the bike like I would a small block chevy in dummy terms I advanced it as much as possible without affecting its ability to start. I advanced it all the way the plate will let me though, so I have to remove the plate and mill all the slots to allow me to rotate it more.

I also turned in the idle screws a lot. They are only about 1 turn out from a soft seat right now.

Took the bike to the gas station since the ignition wasn't cutting out in my garage the whole time I was playing with the timing and syncing the carbs. got me to the gas station no problems. then just didn't want to fire back up to get me home. That was a bit of a long push good thing the gas station is pretty close.

Mean idle though, like a lopey V8 almost. It doesn't just purr it thumps, and on the way to the gas station I gave it a bit of gas and it felt real strong.

Now I guess I'll just have to wait for the new lamp sensors from Newtronic. They said that maybe my lamp sensors are having some kind of heat related issue, so they are sending me some new ones. Hope they don't sit around at customs for a few weeks like the initial kit did.

Pics coming soon, just need to get it photo worthy. Wiring is a bit of a mess right now, it's all just run not tucked