Topic: help me make good decisions building up an 836.

[lofijsc]

Hello,

    I know there are lots already posted on 836 builds but i was hoping to gleen the perfect recipe for my particular needs without scouring the boards. That said . . . I just picked up some good vintage 836 barrels with what seems to be matching 65mm Arias pistons. I wanted to build a stock-ish looking early K with an 836 motor for short tours. So I'm looking for easy freeway speeds with a little more getup then my 736 that i've had for many years (I'm only getting fatter).

    I like spending money as much as the next guy but I do want to do things right. I think the 836 barrels are 77 or 78. I want to use a 78 K head and I have a small pile of bottoms to choose from. I have a set of carbs from a K1. I guess the questions are:

-Is this a good combo (head, barrels and carbs)?
-What modifications should I consider for the head?
-What overall modifications should I consider?
-What should I be afraid of going into this?

Many thanks up front for years of rock solid information.

[Stev-o]

First off welcome.

Sounds like you off to agood start - you know what you want.   Head porting is highly recommended, forum member MRieck has a great reputation for this or APE in Cali could do it.
There is an 836 piston kit on eBay for $110 that is good for a budget build. They are Japanese made, not Chinese.

I'm sure others will chime in with some other good info.

[lofijsc]

Thanks Stev-o

You don't think I should use the Arias pistons that came with the barrels?

[Stev-o]

Thanks Stev-o

You don't think I should use the Arias pistons that came with the barrels?

Not saying you shouldn't, just throwing  out another option. Did you get rings with them?

[Really?]

Tagging along. I may have to go this route with my dead motor.

[MCRider]

Thanks Stev-o

You don't think I should use the Arias pistons that came with the barrels?

Are these new parts? If the ARIAS are bored to the vylinders you probably wouldn't want to consider other pistons.  If the barrels need to be bored, then whatever.

[lofijsc]

these are not new parts, they are definately old used parts. The cylinders look great. I will have my machinest check them out but I'm thinking they just need a hone.

[lofijsc]

The pistons do have the old rings on them

[Stev-o]

these are not new parts, they are definately old used parts. The cylinders look great. I will have my machinest check them out but I'm thinking they just need a hone.

Can you post pics?

[lofijsc]

it wont let me post pics

[Really?]

5 posts and then you can add pics. The spammers forced that rule.

[lofijsc]

Tagging along. I may have to go this route with my dead motor.

I have feeling this thread isn't going anywhere

Maybe you should do one and i can follow yours 

Am I doing something wrong or just impatient?

[MCRider]

Tagging along. I may have to go this route with my dead motor.

I have feeling this thread isn't going anywhere

Maybe you should do one and i can follow yours 

Am I doing something wrong or just impatient?

Frankly you got most of your answers. OK to use used parts in my book, but would turn off a lot of purists. If you do use used pistons and rings, I'm assuming this is a budget piece? Just do a budget valve job, (lapping) replace all the rubber bits, nail it back together per the manual and go ride. It should be fine. We can help with specifics as they come up. No sense in writing a book here that's already been written many times before.

[wrenchmuch]

Honing those barrels is only going to open the end gap on the old rings . This will cause some compression loss . How much loss is reliant on how much the end gap opens . Honing will increase bore diameter and the rings will wear away slightly as they bed in . I don't know if it will be easy to find rings for the arias . I run a Wiseco 836 kit . The added compression and displacement makes for added heat . I like my engine very much but its not for stop and go driving . There are cheap 836 kits on ebay . These cost around $110 us and have lower compression making them a better choice if you do a lot of city driving . If you haven't already check the FAQ section on "where to get parts for my bike " . APE has many great kits for 750 big bores and is a site sponser . Cycle X is another great supplier of parts for our bikes . Dynoman also sells 750 parts . I'm betting by the time you find rings and buy them you'll be into more money than if you bough the ebay kit (possible machine work aside ).
Good luck

[MRieck]

You have to see if you can get rings for the pistons. you have to check skirt to wall....they used to run those loose. You can take up skirt slack with skirt coatings. You want a cam with that....there are many to chose from though I like Megacycle. One of the 63 Web's would be OK. Oversize intake work very well with that size pistons as the larger bore deshrouds the valve getting more charge in. It is important to enlarge the throat area to 90% of the OD of 33.5 mm intake. I'd recommend decking the cylinder and milling the head to insure they are flat. I'd use a thin MLS base gasket to get the piston higher in the bore to improve squish. I'd use a .030 MLS head gasket too. Porting works very well especially thinning the guide boss area and working the short side entry to the seat. You need a good valve job. Check the guides carefully....the exhaust ( at the least) are usually shot.

[MCRider]

Ta Da! 

[Stev-o]

Information overload! 

[lofijsc]

You have to see if you can get rings for the pistons. you have to check skirt to wall....they used to run those loose. You can take up skirt slack with skirt coatings. You want a cam with that....there are many to chose from though I like Megacycle. One of the 63 Web's would be OK. Oversize intake work very well with that size pistons as the larger bore deshrouds the valve getting more charge in. It is important to enlarge the throat area to 90% of the OD of 33.5 mm intake. I'd recommend decking the cylinder and milling the head to insure they are flat. I'd use a thin MLS base gasket to get the piston higher in the bore to improve squish. I'd use a .030 MLS head gasket too. Porting works very well especially thinning the guide boss area and working the short side entry to the seat. You need a good valve job. Check the guides carefully....the exhaust ( at the least) are usually shot.

-I didn't expect the rings to be unique to the piston manufacturer. . . thanks for the heads up
-I will be relying on a machinest to tell me if the pistons, barrels and head can come together right. I fully expect bad news along the way.
-I am interested in keeping a relatively flat power band and I dont expect to ever pop 8k on the tach. I'm really not sure which cam to get or how much porting I should do. Would I be better off getting an F2/F3 head for the larger valves?
-I was prepared to replace the valves, guides and springs because I ssumed I would need to step them up. If the stockers check out should I just leave them?

[MRieck]

You have to see if you can get rings for the pistons. you have to check skirt to wall....they used to run those loose. You can take up skirt slack with skirt coatings. You want a cam with that....there are many to chose from though I like Megacycle. One of the 63 Web's would be OK. Oversize intake work very well with that size pistons as the larger bore deshrouds the valve getting more charge in. It is important to enlarge the throat area to 90% of the OD of 33.5 mm intake. I'd recommend decking the cylinder and milling the head to insure they are flat. I'd use a thin MLS base gasket to get the piston higher in the bore to improve squish. I'd use a .030 MLS head gasket too. Porting works very well especially thinning the guide boss area and working the short side entry to the seat. You need a good valve job. Check the guides carefully....the exhaust ( at the least) are usually shot.

-I didn't expect the rings to be unique to the piston manufacturer. . . thanks for the heads up
-I will be relying on a machinest to tell me if the pistons, barrels and head can come together right. I fully expect bad news along the way.
-I am interested in keeping a relatively flat power band and I dont expect to ever pop 8k on the tach. I'm really not sure which cam to get or how much porting I should do. Would I be better off getting an F2/F3 head for the larger valves?-I was prepared to replace the valves, guides and springs because I ssumed I would need to step them up. If the stockers check out should I just leave them?

No. Springs and valves should be replaced. CycleX ( and myself) sell sets with the OS intake for short money. The guides have to be checked like I said earlier. A Web 41A will keep the compression, and consequently, the torque up.

[lofijsc]