Topic: Cheap 836 kits back on ebay...$110! *Update!

[scottly]

Cool!! When does the rebuild start? An AZ summer project??

[jacquesleclochard]

Went overboard and ordered 4 kits (two for a friend), 1 carb rebuild kit and a few brake pads. It's not like I have money to spare, it's just that... it all looks so GOOD, and so CHEAP!! 

The seller is really entheusiastic and clear in his communication. Now let's put some miles on that project (ffw 5 months?)

[Terry in Australia]

I think Terry in Australia hoarded up a few. Maybe he has tried one now.

G'Day Eric, I bought a couple of sets last year, the quality looks quite good, but I sold them both to a couple of local CB750 nuts so I haven't tried them out. I might have to buy some more. Cheers, Terry.

[gschuld]

Could someone give me an idea as to what compression ratio I would end up with if I used this kit(which I just ordered ) in a 76 cb750f engine?  It doesn't seem like it would be very high.  Any idea as to how much I can reasonably increase the CR with head milling, etc? 

Thanks

[HondaMan]

Could someone give me an idea as to what compression ratio I would end up with if I used this kit(which I just ordered ) in a 76 cb750f engine?  It doesn't seem like it would be very high.  Any idea as to how much I can reasonably increase the CR with head milling, etc? 

Thanks

They come in at about 9.5:1 compression if you do not modify the head to add a quench band. If you add the quench band, it drops to about 9.25:1, depending on how much you taper the edges of the chamber. Don't forget: you are increasing the displacement by about 14% with these pistons, while the chamber remains the same as for the 736 engine.

The Wiseco pistons, with their domes, come in at an advertised 10.5:1 at 836cc, but that number presumes an untouched chamber. It makes for a lot of extra heat and a tendency to knock at low octanes, so the lower CR of these pistons is a good bet for trouble-free riding.

[longshanks]

These guys claim 10.5 compression from their kit. Is this any better than the ones from cruzin.co?

http://cgi.ebay.com/ebaymotors/Honda-cb750-849cc-Big-Bore-Kit-Cafe-Vintage-/200592968530#ht_561wt_941

[Terry in Australia]

The CycleX 850 kit is good if you've got a worn out 836, but looking at how thin your cylinder sleeves are when bore out to 836cc, I worry about losing another .5mm from already very thin (2mm thk) cylinder walls? I'd buy the 110 dollar kit, unless I needed to reclaim an old set of 836cc sleeves. Cheers, Terry.

[wannabridin]

I just ordered a set!  I'm still going to go with my 4th over kit, but this will be nice to have if I change my mind or decide to go bigger later...  Thanks for the link!!  I missed out the last time around by about a day, so I jumped on it now!

[gschuld]

Quote from: gschuld on June 05, 2011, 08:44:36 pm

Could someone give me an idea as to what compression ratio I would end up with if I used this kit(which I just ordered ) in a 76 cb750f engine?  It doesn't seem like it would be very high.  Any idea as to how much I can reasonably increase the CR with head milling, etc? 

Thanks


From Hondaman:

They come in at about 9.5:1 compression if you do not modify the head to add a quench band. If you add the quench band, it drops to about 9.25:1, depending on how much you taper the edges of the chamber. Don't forget: you are increasing the displacement by about 14% with these pistons, while the chamber remains the same as for the 736 engine.

The Wiseco pistons, with their domes, come in at an advertised 10.5:1 at 836cc, but that number presumes an untouched chamber. It makes for a lot of extra heat and a tendency to knock at low octanes, so the lower CR of these pistons is a good bet for trouble-free riding.



Thank you Hondaman, just what I wanted to hear!

[HondaMan]

The CycleX 850 kit is good if you've got a worn out 836, but looking at how thin your cylinder sleeves are when bore out to 836cc, I worry about losing another .5mm from already very thin (2mm thk) cylinder walls? I'd buy the 110 dollar kit, unless I needed to reclaim an old set of 836cc sleeves. Cheers, Terry.

I used to worry about that back in the 1980s when the 836 kits got so popular, fearing that riders would come back with bent rods and such nightmares. With the exception of those riders who would have done that with even the stock engines, I have been surprised to see how many of the 836 engines have been in touring and commuting service for 20+ years since, some with 50k miles on them and no new oil leaks (noting that those dry engines also had the HD cylinder studs from RC or Action Fours installed). The driest ones are the K3 and later engines with the fancier head seals. Also, those engines that were "built" and at the same time received professional valve jobs (often new guides on post-1974 engines) seem to have done the best.

I think I'd have to tip my hat to Sochiro for that design.

[longshanks]

The CycleX 850 kit is good if you've got a worn out 836, but looking at how thin your cylinder sleeves are when bore out to 836cc, I worry about losing another .5mm from already very thin (2mm thk) cylinder walls? I'd buy the 110 dollar kit, unless I needed to reclaim an old set of 836cc sleeves. Cheers, Terry.

Is it necessary to re-enforce the sleeves when boring out to 836 with this kit?

[longshanks]

If I bought the kit now would it still be good if it sat stored in a cool, dry place for a year or so until I'm ready to re-build??

[Retro Rocket]

If I bought the kit now would it still be good if it sat stored in a cool, dry place for a year or so until I'm ready to re-build??

Yes i have 3 kits in "storage" {not these ones}. They will keep forever if in the right conditions....

[That 70s Bike]

Thanks to all the positive comments here I finally pulled the trigger on a set + a spare ringset and headgasket.

[Terry in Australia]

The CycleX 850 kit is good if you've got a worn out 836, but looking at how thin your cylinder sleeves are when bore out to 836cc, I worry about losing another .5mm from already very thin (2mm thk) cylinder walls? I'd buy the 110 dollar kit, unless I needed to reclaim an old set of 836cc sleeves. Cheers, Terry.

Is it necessary to re-enforce the sleeves when boring out to 836 with this kit?

You can't mate. CycleX do sell thicker sleeves for 836-900 kits, but you'll need to take your cylinder block and top engine case to an engineer to get them bored out to accept the thicker sleeves. Like Hondaman says, there are plenty of 836cc bikes out there that haven't destroyed themselves, (although I don't think it's that much of a design feat for an engine to handle a relatively small displacement increase) so I wouldn't be too fussed about it. Just use a good set of APE Heavy Duty cylinder studs, the OEM studs are barely capable in a stock 750 engine. Cheers, Terry.

[longshanks]

The CycleX 850 kit is good if you've got a worn out 836, but looking at how thin your cylinder sleeves are when bore out to 836cc, I worry about losing another .5mm from already very thin (2mm thk) cylinder walls? I'd buy the 110 dollar kit, unless I needed to reclaim an old set of 836cc sleeves. Cheers, Terry.

Is it necessary to re-enforce the sleeves when boring out to 836 with this kit?

You can't mate. CycleX do sell thicker sleeves for 836-900 kits, but you'll need to take your cylinder block and top engine case to an engineer to get them bored out to accept the thicker sleeves. Like Hondaman says, there are plenty of 836cc bikes out there that haven't destroyed themselves, (although I don't think it's that much of a design feat for an engine to handle a relatively small displacement increase) so I wouldn't be too fussed about it. Just use a good set of APE Heavy Duty cylinder studs, the OEM studs are barely capable in a stock 750 engine. Cheers, Terry.

Thanks Terry, cylinders studs such as these?    http://www.z1enterprises.com/detail.aspx?ID=3979

[knowsnothing]

The CycleX 850 kit is good if you've got a worn out 836, but looking at how thin your cylinder sleeves are when bore out to 836cc, I worry about losing another .5mm from already very thin (2mm thk) cylinder walls? I'd buy the 110 dollar kit, unless I needed to reclaim an old set of 836cc sleeves. Cheers, Terry.

Is it necessary to re-enforce the sleeves when boring out to 836 with this kit?

You can't mate. CycleX do sell thicker sleeves for 836-900 kits, but you'll need to take your cylinder block and top engine case to an engineer to get them bored out to accept the thicker sleeves. Like Hondaman says, there are plenty of 836cc bikes out there that haven't destroyed themselves, (although I don't think it's that much of a design feat for an engine to handle a relatively small displacement increase) so I wouldn't be too fussed about it. Just use a good set of APE Heavy Duty cylinder studs, the OEM studs are barely capable in a stock 750 engine. Cheers, Terry.

Thanks Terry, cylinders studs such as these?    http://www.z1enterprises.com/detail.aspx?ID=3979

Those would be them.

[HondaMan]

If I bought the kit now would it still be good if it sat stored in a cool, dry place for a year or so until I'm ready to re-build??

Yes i have 3 kits in "storage" {not these ones}. They will keep forever if in the right conditions....

Is that part of your 'retirement plan'?

[gnarlycharlie4u]

I wouldn't be afraid of these a bit. These aren't big HP high compression machines. Cheap pistons should hold up fine. Besides, cheap piston now are surly as good as factory piston 40 years ago, and they're are loads of bike still running with those OE pistons and rods.

That's very bad logic IMO.

haha agreed. I'd take a 40 year old honda cast piston over a questionably cast/heavier/needs deburring piston anyday.

i am curious about these though.

[Elan]

Well I bought the kit, got bored, engine is assembled, and im hoping for a first start by next week. Ill let you know if it blows up.

[Retro Rocket]

If I bought the kit now would it still be good if it sat stored in a cool, dry place for a year or so until I'm ready to re-build??

Yes i have 3 kits in "storage" {not these ones}. They will keep forever if in the right conditions....

Is that part of your 'retirement plan'?

At the rate these bikes are appreciating it may not be that bad of an idea.....

[wannabridin]

Thoughts on using these versus Z1's 4th over kit that I'm already bored out to??  MRieck thinks they're good for 5 extra hp...  Thoughts??

[wannabridin]

Any advice?

[jacquesleclochard]

Hot diggity dog, they're sitting at customs for a week now. Good heavens. I hope I won't have to pay a lot of import taxes.

Elan, did you blow up already? How's tricks?

[Elan]

Hot diggity dog, they're sitting at customs for a week now. Good heavens. I hope I won't have to pay a lot of import taxes.

Elan, did you blow up already? How's tricks?

Trying to get this oil pump primed. Engine is turning over nicely. The machinist I used did a great job. It was through ebay, about $150 shipped.  Also waiting for float bowl screws. Hopefully this weekend!