Topic: Building an endurance engine

[livefast_dieold]

So here I am. I'm not disappear, I've just been quite busy.

So far I've working on the rod and on the head.

Pics, of course:





Rods: -20 grams each. I've working on them also to improve fatigue strength by remove all the sharp notches (where the cracks start and propagate). I don't think I'm gonna polished them because, frankly speaking, it's a pain in the ass, even if it will very improve fatigue strength. Some nights ago I was starting polishing, but after a couple of minutes with sand paper I remember how many hours I'd spent on the CB500 rods and thought that it will much better to spend that hours dating girls. A heavy sandblast will do the job and increase fatigue strength too. I've balanced them, of course.

Intakes: just a nice refinement, nothing extreme. I think I'm quite limited by the tool I'm using (a dremel). It takes a lot of time to remove the aluminium. I'm wondering what tools the pro use, any idea?  The final surface treatment will be a light sandblast..

Now, speaking what I will do next and what parts I'm gonna buy.

I've developed my personal recipe, which I hope at the end will result in a fast, cheap and reliable bike (I'm a dreamer, I know).
I hope to remain in a budget of 2000 euros (money that I gained by give math and physic lessons to high school and university students  ).

So here's the engine recipe:

-carbs: I'm thinking to fit the carbs of a '80 bike. I saw a lot of mikunis and keihins in ebay for less than 100 euros, too bad they are depression carburetors. What diameter do you suggest? I was thinking 30 or 32, or maybe can I go up to 35?

-cams: I will regrind the original. I have to do some calculations about, but think I will stay with a classic 20-50/50-20 configuration and adding an extra mm to the lift. (maching cost: around 100 euros)

-crank: lighter as far as it's possible (i don't know exactly how much it's possible  )

-titanium retainers (cost? available in Europe?)

-pistons: that's an issue. I have to stay in the 750 class. (cost? available in Europe?)

-Dyna ignitions and coils

That's all now.

Stay tuned 

[kslrr]

Good luck on your project.  I like how you think: work on the basics.

[bucky katt]

if this is a 750 we're talking about, i'd go with a set of carbs from either an early kz900 or kz1000 i believe the mikunis on those are 29mm, a little larger than the stock 750 carbs but a much better carburetor.

[voxonda]

Hey Livefast_dieold,

Good to see people interested in endurance racing. Also busy with building engines for endurance, but go up to 1000cc with one of them and 850 with the other. Good to see you do a lot yourself.
I you want parts, like the retainers, give me a PM.
Regarding the carbs, the Kawi/mikuni a good but so are the originals, maybe not that good, and you can play with them too.
BTW. Did you weigh your crankshaft without rods? What was it? Forgot how much mine weighed. It is now 8.5 kg.
And do not hold back on the pictures!

Rob

[livefast_dieold]

Hey Livefast_dieold,

Good to see people interested in endurance racing. Also busy with building engines for endurance, but go up to 1000cc with one of them and 850 with the other. Good to see you do a lot yourself.
I you want parts, like the retainers, give me a PM.
Regarding the carbs, the Kawi/mikuni a good but so are the originals, maybe not that good, and you can play with them too.
And do not hold back on the pictures!

Rob

Thanks Rob. I saw your nice site, I will definitely set an order after Xmas. About the crank: how much weight do you have taken off from yours?

Consider that I have a rusty CB900 that will be useful for parts like carbs, front forks wheels ecc...


Riccardo

[voxonda]

See my reply, mine weighs 8.5 kg now. Do you know what your weigh now?

Rob.

[livefast_dieold]

See my reply, mine weighs 8.5 kg now. Do you know what your weigh now?

Rob.

sorry I skip that line  I don't measured it yet...hope to have some spare times in this weekend to do some other works.

Thanks
Riccardo

[turboguzzi]

ciao ricc

by the late 70's most bikes were moving on to CV carbs ("depression carbs" is a very italian term  ) so its hard to find any piston type carbs above 28mm. I cant think of any in-line four that had round piston type carbs bigger than 28-29. The best stock production carbs are the VM28 SS of big kawasakis, but i doubt very much you'll find them for 100 euro. early gsxr750 had 29mm flat slides but these are illegal for vintage.

There were works hondas that raced with CV carbs but before going for that, check that these carbs are OK with our rule book. You will also find less info about how to tune them, at least in this forum. the positive note is that you will find them in any size you want and they are very light too.

these guys are your best source for tuning CV carbs

http://www.factorypro.com/tech_tuning_procedures/tuning_carbtune,CV,high_rpm_engines.html

and BTW, I guess you dont want to "sand blast" your rods but rather "bead blast" with iron balls.....

speak with member KOS for your 750 pistons.

[Retro Rocket]

Hi TG,

early gsxr750 had 29mm flat slides but these are illegal for vintage.

How would these carbs go on a hotted up 750/4.? What would they be like compared to CR29's..

Sorry for the hijack.

Mick

[turboguzzi]

Hi TG,

early gsxr750 had 29mm flat slides but these are illegal for vintage.

How would these carbs go on a hotted up 750/4.? What would they be like compared to CR29's..

Sorry for the hijack.

Mick

never said I tried...... but for someone who's not limited by vintage rules, might be worth trying. being flat slide they are certainly more advanced than CR's and I'd guess way cheaper too.

[mlinder]

Flatslides have their positive and negative points. Not the best for street riding, in my opinion. There is much more of an on/off characteristic with them, in most applications.

[turboguzzi]

Flatslides have their positive and negative points. Not the best for street riding, in my opinion. There is much more of an on/off characteristic with them, in most applications.

+1

i had many years ago a first series GSXR750 with its original flat slides. The bike was VERY on-off,

coming alive with a bang at 5000 rpm.

i followed a common solution then, fitting later gsxr 38mm CV carbs and the bike became a pussycat without losing much top-end if any.

boy, how I miss that bike, every now and then i check the ads and there's a mint one for sale nearby at 1800..... its really calling me.

[livefast_dieold]

ciao ricc

by the late 70's most bikes were moving on to CV carbs ("depression carbs" is a very italian term  ) so its hard to find any piston type carbs above 28mm. I cant think of any in-line four that had round piston type carbs bigger than 28-29. The best stock production carbs are the VM28 SS of big kawasakis, but i doubt very much you'll find them for 100 euro. early gsxr750 had 29mm flat slides but these are illegal for vintage.

There were works hondas that raced with CV carbs but before going for that, check that these carbs are OK with our rule book. You will also find less info about how to tune them, at least in this forum. the positive note is that you will find them in any size you want and they are very light too.

these guys are your best source for tuning CV carbs

http://www.factorypro.com/tech_tuning_procedures/tuning_carbtune,CV,high_rpm_engines.html

and BTW, I guess you dont want to "sand blast" your rods but rather "bead blast" with iron balls.....

speak with member KOS for your 750 pistons.

Thanks for the info! I owe you a beer 

[livefast_dieold]

Hi there! I'm still quite busy here. I'm ending the head and went for a complete hemispheric combustion chamber (hondaman's trick  ), plus I went for a little more extreme porting which means more hours at the dremel.



I'm not an expert of CB750 parts and differences between the models, but during these days I saw a lot of pics of OEM pistons and mine are not like them! Although they are from Honda,they have a thin and flat dome on the top. Diameter is 60.45 mm (worn, according to the manual). Engine number is CB750E 2553894, frame number is 2096426. Here's a pic:



Good news: my father got interested in my endurance project and he eventually sponsors me  I hope this means keihin CR!


GOOD NEW YEAR'S EVE TO EVERYONE 

[voxonda]

Hey livefast_dieold,

That is a F1 piston/engine. Same as I have, among the K6,K7 and F2(2x)

Happy New Year!

Rob

[lordmoonpie]

Riccardo,

here's a pic of the piston you can get from Mark at M3 (kos) for you to compare - looks like apples and oranges to me 

[Howell]

Cheep tricks to build a fast and reliable engine:

I have two tuned engines , one with 860 cc, this is a F2 engine.
Therefore we use second hand Kawasaki KZ750/4 pistons (66mm)
Sleeves from a CB900.
Also CB900 rods.
Camshaft from Webcam.
Also we use bigger inlet valves (35MM) from a Mitsubishi Lancer.
Home made titanium valve retainers.
Kibblewithe valve springs and Ape studs.
The head is  flowed and ported and as you can see on the picture there is put some extra alu in the ports to become the right flow.
Even the ports have a rough surface for having a good mixture of the air and petrol , you must have a swirl , do not polish them !

At the moment I am riding with a 822 cc engine (F2)
Second hand pistons from a CB900.
Also a ported head the same way as the 860cc.
Only bigger inlet valves 35 mm.
The cam , the rods, valve springs and retainers are stock Honda.
I use Keihin CR31 mm carbs.
This engine is very fast and reliable.

The 860cc engine I have n't tried yet

So here some pictures of the engine parts.

[Old Scrambler]

VERY TRICK Howell.........are you saying the valves are a direct swap?  or what had to be modified?  What do you use for a camchain and tensioner?

[Howell]

VERY TRICK Howell.........are you saying the valves are a direct swap?  or what had to be modified?  What do you use for a camchain and tensioner?

It is not possible to swap the valves directly, the stem of the Mitsubishi valve is longer , so you have to shorten it and then have to make the splines for the cotter valves.
After shortening you must harden the top of the valve stem.Welding stainless steel on it.
I use the stock camchain and tensioner, all new.
But I  made a small plate under the primary tensionerspring to get more tension on that chain.

[Howell]

Some more cheep trick pictures and the complete bike:

[livefast_dieold]

Thanks for the info and the nice pics! I was wandering if the beatiful things Voxonda and Howell do with the sohc honda are due to the legal weed or if something else 

[andy750]

This is excellent info Howell and fantastic photos. Its also good to know your 822cc engine is superfast as I am currently going the 812cc route. Hoping for the same.

thanks
Andy

[wannabridin]

howell, can you explain why the use of the CB900 pistons vs. some weisco or APE 836cc ones?  was it just for cost?  also, what year pistons do you recommend?

[Howell]

howell, can you explain why the use of the CB900 pistons vs. some weisco or APE 836cc ones?  was it just for cost?  also, what year pistons do you recommend?

Well, that are mainly the costs , I  buyed the Cb900 pistons with rings for only  $25,= on Ebay , also the Kawa pistons and many other things.
Example now on Ebay pistons and rods for only $69,= : http://cgi.ebay.com/ebaymotors/1982-honda-cb900-cb-900-custom-pistons-and-rods_W0QQitemZ260388577339QQcmdZViewItemQQptZMotorcycles_Parts_Accessories?hash=item3ca05e603b
All pistons of a CB900 are good , mine are from a CB900 custom from 1982.
We clean them and also sandblast them a little bit , but pay attention to the rings when they are worn you have to replace them.
Mostly when a bike uses much oil it are not the pistons or rings but the sleeves are then a little bit oval.
When you use these pistons you can also use the original Cb750 sleeves but you must bore them out to the right size.
Also you have to make new valve pockets otherwise the valves hits the pistons.

[livefast_dieold]

Inspired by Howell's piston swapping I made some research to find out if there are some japan bikes with pistons of 62 mm dia. (so i will stay in the 750 class).
The kawasaki KZ650 have pistons of that size, with a very nice dome on the top and valve pockets. Now I'm tring to discover another important size: the wrist pin diameter! Anyone knows that? Because I remeber that some kawasaki have a 14mm dia wrist pin, maybe I can bore that size to the 15mm that honda uses.