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Author Topic: Project "walrus" Yam XS 750  (Read 30021 times)

Offline datadavid

  • Posts: 1072
Re: Project "walrus" Yam XS 750
« Reply #10 on: Aug 01, 2016, 15:17:06 »
show me yours i'll show you mine 😀
so these are my main and pilot jets, this would be the stock jetting of a 78 something model.
42.5 pilot 130 main.
You are going to end up at 140 mains, 142.5 center main is nice also - if you are running open exhaust and good flowing filters. May want to raise the needle one full notch as well, but do that last. I did not need to go up on pilot jets on my stock-ish (pod filters and 2" 3-1 megaphone) 750, it ran perfectly on stock pilot jets.
I run 150 mains and 155 center in mine because its got high comp ratio, full open exhaust and k&n filters besides the extra 150cc 😊

Offline Psycrow

  • Posts: 78
Re: Project "walrus" Yam XS 750
« Reply #11 on: Aug 01, 2016, 17:21:48 »
Also working on an XS750 triple 78' over in the Tracker section... I'll be watching this.. I've delta with Second gear issues on other Yamaha bikes... my understanding is that it's not a terrible job on these... on my 84 FJ1100 it was a complete teardown  and split cases to change two gears and a shift fork... geesh. Unfortunately you will need to drive the bike and load second gear to see if yours has the issue... it's not an expensive fix if you do the work yourself and the bike can still be driven till you decide to do the repair. Your not going to ruin anything else by riding it... just take it easy through 2nd.

Psy

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Online XS750AU

  • Posts: 254
Re: Project "walrus" Yam XS 750
« Reply #12 on: Aug 02, 2016, 07:56:03 »
Mains are: 145´s and idles are 17.5´s...
Am i right that you mean shooting the brake fluid "between" the carbs where the butterlfy axles meet the carb bodies?
I will let the engine run warm and then make an oil change (motor oil and shaft oil).
probably need to change the rubber mounting boots of the carbs too, they look hard and worn,do you know what the stock mixture screw setting is (I write down the turns out of the screws they were 5 1/4 turns out)?

do i need to bench sync the buterflies with some copper wire?
in closed position there seems to be NO gap between carb body and butterflies now...

Hi Ryan
145 mains and 17.5 pilots were standard in some markets, but as Dave has said 130 & 42.5 is a common arrangement.
Not sure about shooting brake fluid - but to check for leaking seals and mounting rubbers I have used carbi cleaner. You can smell it come through the exhaust. The fact that the mixture screws were turned out 5+ turns indicates that the PO had idle problems due to air leaks and they were trying to  make the idle mixture richer. Suggest you get a new set of rubber mounting boots from Yambits in England (cheapest I could find) and butterfly seals from Mike XS. Made a world of difference to my XS750.

At idle there should not be any visible gap between butterfly and body, when the idle speed screw is fully backed off. This may be another pointer that your bike was sucking air through a leak and the PO was trying to get it to idle below 2,000rpm. I had the problem and it has now been fixed by butterfly seals and new rubber mounting boots - it is 40 years old!!!
Good luck
Tim
“Engineering is the art of being approximately right rather than exactly wrong.”

Yamaha XS750-2D
Yamaha XS896
Husaberg FE550
Yamaha TT250
Yamaha IT200N

Online XS750AU

  • Posts: 254
Re: Project "walrus" Yam XS 750
« Reply #13 on: Aug 02, 2016, 08:26:12 »
Hi Ryan
Just looking at the photos and looks like a 2D and they had triple points ignition!!! A bitch to maintain.
Has it been converted to the later CDI???
Don't mean to tell you how to such eggs - but have you tested that you have spark?
Cheers
Tim
“Engineering is the art of being approximately right rather than exactly wrong.”

Yamaha XS750-2D
Yamaha XS896
Husaberg FE550
Yamaha TT250
Yamaha IT200N

Offline Ryan Stecken

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Re: Project "walrus" Yam XS 750
« Reply #14 on: Aug 02, 2016, 13:06:07 »
show me yours i'll show you mine 😀
so these are my main and pilot jets, this would be the stock jetting of a 78 something model.
42.5 pilot 130 main.
You are going to end up at 140 mains, 142.5 center main is nice also - if you are running open exhaust and good flowing filters. May want to raise the needle one full notch as well, but do that last. I did not need to go up on pilot jets on my stock-ish (pod filters and 2" 3-1 megaphone) 750, it ran perfectly on stock pilot jets.
I run 150 mains and 155 center in mine because its got high comp ratio, full open exhaust and k&n filters besides the extra 150cc 😊

thanks datadavid for your input!

looks like you have different carbs...my mains and idles are installed in the float bowls...looked it up and my settings are stock for my model...

Offline Ryan Stecken

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Re: Project "walrus" Yam XS 750
« Reply #15 on: Aug 02, 2016, 13:07:16 »
Hi Ryan
Just looking at the photos and looks like a 2D and they had triple points ignition!!! A bitch to maintain.
Has it been converted to the later CDI???
Don't mean to tell you how to such eggs - but have you tested that you have spark?
Cheers
Tim

thanks for your insight tim!
the PO converted it to the 850 cdi setup...i have strong spark.this was one of my concerns...is it possible that the timing is off, even when the PO installed a cdi?if yes how can I check?

Offline Ryan Stecken

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Re: Project "walrus" Yam XS 750
« Reply #16 on: Aug 02, 2016, 15:30:53 »
I have another question guys concerning the stock brakes:

They are stuck so i'll nees to get them off and give them a good clean...there are three bolts holding the brakes,one has some kind of a rubber dampening to the screw...what is that screw doing?is it also holding the brake on the fork?
Just wanted to ask tou guys before i break something precious ;-)

Online XS750AU

  • Posts: 254
Re: Project "walrus" Yam XS 750
« Reply #17 on: Aug 02, 2016, 18:30:37 »
Hi Ryan
Difficult to install cdi the wrong way. The main thing to check is that the rotor is correctly engaged in the idex pin on the end of the crank. Also check that the index pin has not been push flush with the crank. Should run at that point, then you need a timing light to get the coil plate exactly correct.
Brakes, 2 bolts hold the brake assembly to the forks, undo first. The bolt with rubber damper  allows the caliper to float and self align with the disc. You can rebuild without removing. but if you are re building pull apart and make sure the caliper can slide on bolt.
Cheers
Tim

Sent from my GT-I9506 using Tapatalk

“Engineering is the art of being approximately right rather than exactly wrong.”

Yamaha XS750-2D
Yamaha XS896
Husaberg FE550
Yamaha TT250
Yamaha IT200N

Online XS750AU

  • Posts: 254
Re: Project "walrus" Yam XS 750
« Reply #18 on: Aug 02, 2016, 19:44:15 »
Hi Ryan
You say your jets screw into the float bowl! That sounds like the Hitachi carbies used on the 850. The 850 cdi is great as it has electronic advance, but the Hitachi carbs have a bad rap. Hard to get parts including jets. What brand is marked on them?
What carbs are on the other bike, they may be a better option. Makuni series II with the 2 position choke are the best factory carb unless you go the triumph option. If you go the triumph option you will need to rejet as yours is a 750 and the triumph triples with carbs were 900.
Regards
Tim

Sent from my GT-I9506 using Tapatalk

“Engineering is the art of being approximately right rather than exactly wrong.”

Yamaha XS750-2D
Yamaha XS896
Husaberg FE550
Yamaha TT250
Yamaha IT200N

Offline datadavid

  • Posts: 1072
Re: Project "walrus" Yam XS 750
« Reply #19 on: Aug 03, 2016, 08:20:34 »
Yes throw the hitachis as far as you can. Not worth the bother.