I stepped in it - XS750/896 build

[Frenchtom]

 

[Frenchtom]

 

[Frenchtom]

I did have one valve seat that looks lightly damaged and pitted like something got sucked through and was pinched by the valve a few dozen times before it left the engine. I am hoping that lapping the valves will smooth out the pitting.

 

[pidjones]

I did have one valve seat that looks lightly damaged and pitted like something got sucked through and was pinched by the valve a few dozen times before it left the engine. I am hoping that lapping the valves will smooth out the pitting.

Lapping those marks will just destroy the valve, I fear (but, it is probably already destroyed by the foreign matter). That should be recut.

 

[pidjones]

The valve is probably destroyed, anyway.

 

[Frenchtom]

Been a while but I have made some progress. The cases are painted and the cylinder is installed. That was an interesting struggle to say the least. I also lapped the valves and it passed the water leak test with flying colors. Next I will remove the solid state timing and adjust its setting along with painting more of the engine exterior.

 

[Frenchtom]

Too long since last update. Added a new front tire, installed the engine with a new digital electronics system, new handlebars, rebuilt and re-jetted the carbs, rebuilt the starter, and painted a bunch of stuff. Now I am trying to get my calipers un seized. I was really surprised how bad of shape they were in given that they looked so clean and ready for use on the outside. Also have a new battery, handgrips and a bunch of goodies on the way. I'll cut the handle bars back a bit and try to get the bike running before year-end.

 

[XS750AU]

It is looking good.
What carbies are you using and where did you start with your jetting?
What air cleaners are you going to run?

 

[Frenchtom]

It is looking good.
What carbies are you using and where did you start with your jetting?
What air cleaners are you going to run?

I have the stock Mikunis from the original 750 engine. I think I went 165 main jet and 47.5 primary jet but thinking about that now, those might be too big. I have not decided on the air cleaner. I have the stock air cleaner box and I may try to put high flow filters inside or I may roll the dice and go pods. Pods are hit or miss and I do not want an unreliable bike. I may even try and build a new air box with pods inside.

 

[XS750AU]

You are definately going to have to go bigger than 750 stock, so I guess you have a starting point. If you do happen to find a set of carbies off a Triumph 900 triple they bolt staight on and I did not need to touch the jetting. Most people prefer the Keihin carbies but I found a set of the earlier Mikuni flatslides and rebuilt them for very little cost.
Do you know which version of Mikunis you have? The later version are supposed to be better than the first version and the Hitachi used on the 850 are to be avoided due to difficulty in getting parts.
Once you get this bike going you will not regret the work. The 896 bigbore transforms the bike from average to whow! The only problem is you run out of gears at 200Km/h, if that really is a problem!!!!

 

[Frenchtom]

You are definately going to have to go bigger than 750 stock, so I guess you have a starting point. If you do happen to find a set of carbies off a Triumph 900 triple they bolt staight on and I did not need to touch the jetting. Most people prefer the Keihin carbies but I found a set of the earlier Mikuni flatslides and rebuilt them for very little cost.
Do you know which version of Mikunis you have? The later version are supposed to be better than the first version and the Hitachi used on the 850 are to be avoided due to difficulty in getting parts.
Once you get this bike going you will not regret the work. The 896 bigbore transforms the bike from average to whow! The only problem is you run out of gears at 200Km/h, if that really is a problem!!!!

I do not know how to figure out which Mikunis I have. There is very little writing on them. Does a picture help?

 

[XS750AU]

What does the choke lever look like? That is the easiest way to tell.

 

[Frenchtom]

Hope these are at the right angle. Thanks for the help!

 

[XS750AU]

OK - they are the Mk1 version. If you have rebuilt and they work, then all good. If they give trouble then it might be worth looking for a set of Triumph 900 carbies.
I have not worked on the Mk1 version. I have MkII on my 750 and the Mikuni flatslides on my 896.

 

[HollywoodMX]

I'm surprised they are a direct swap. Get the 900 carbs. Free hp, screw that old crap. Yamaha was really concervative with carbs back then leaving ponies on the table.

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