Topic: F2 tuned engine buying tips

[Henkies]

Hi,

Hopefully I'm placing this in the correct section.
I'm about to buy a CB750 F2 engine to put in my K7. But I'm new to 4 strokes, coming from 2t motocross.

What should I pay special attention to when visiting the seller? I.e. Typical F2 flaws and rebuild aspects.
And which carbs do you advise for street use? I do have the k7 carb's of course.

This is the setup of that engine, hasn't even been driven yet:
- JE 836cc JE Pistons, compressions 10,5:1
- Web-cam Stage 2 camshaft
- Kibblewhite Black Diamond Stainless valves.
- Adjustable timing wheel, reinforced chain.
- Carrillo H beam crankshaft rods.
- crankshaft lightened and balanced.
- Gas-flowed head
- Bronze valve guides, APE springs, Titanium valve retainers.
- ARP cilinder bolts and nuts
- new gaskets, seals, bearings, tensioners

Thanks!

[Jerry Rxman Griffin aka MuthaF'er]

Is this what you are doing or what you are buying?

[Henkies]

Buying

[MessnerMoto]

How much ?

[calj737]

That would appear to be a very strong motor. The only way to verify those things is through receipts, and of course with a written guarantee. It looks as though you're from Europe, so if you provided some background on who/where the motor is coming from, perhaps a member here is familiar with the Seller and can attest to their reputation/integrity.

I'm unclear if any upgrades on the Cam Chain/Tensioner, or Cam towers/bolts, and Primary Chain components were also upgraded.

[Jerry Rxman Griffin aka MuthaF'er]

Make him pull the valve cover off. Retainers would be obvious. adjustable cam sprocket would be obvious. cam might be obvious depending on markings. If no markings on the shaft remove the end retainer washer and look there.

Pull the oil pan. Lightened crank and Carrillo rods would be obvious.

Pull a spark plug and make sure he hasn't used K flat top pistons in that engine.

That's some serious money so don't just take his word for it.

[754]

 I agree with Jerry  had too many surprises in my motor buying.

[Henkies]

Thanks, good suggestions. Would you guys advise to rejet the k7 carb or put larger carbs one it, for street use? Just in case: don't have much budget left

[PeWe]

Check compression so it will be around 175 PSI or more. Too low CR pistons might end in 140 PSI area.
Cam used will affect the PSI too. Wide open long duration cam need more CR to compensate.

[Jerry Rxman Griffin aka MuthaF'er]

Don't worry about the carbs until you know what you actually have. Yes, if it is what it is supposed to be, it can handle larger carbs but do you really need to since it can also handle the stock carbs if properly jetted. If you have US$1000 extra to drop on carbs what the hell, go for it.

[Henkies]

OK I bought it.
Compression test wouldn't be valid, as the engine wasn't built in. Het got some packaging, calculations and former parts left.
I could see the following. Thanks for your help!

- I can see it has brand new domed pistons with valve clearance.
- New Black valves
- Web-cam 63a camshaft and rockers redone (hard welded, according seller)
- Adjustable timing wheel, new chain tensioner.
- Carrillo H beam crankshaft rods.
- Flowed head, but don't know wether it's good.
- Bronze valve guides, new springs and valve retainers.
- HD cilinder bolts and nuts
The crankshaft wasn't really lightened, balanced only.

[Jerry Rxman Griffin aka MuthaF'er]

Sounds like a good and a pricey engine. 

[dragracer]

That's a good package of parts. Hopefully you got a nice deal without paying for the sum of the parts used in the build.

[Sam Green Racing]

What diameter are the valve stems ?

[Henkies]

I meassure approx 6.5mm at the end of the stem. As I see now, that are no High Performance 5mm stems? Don't see colored valve stem seals either, they're just black.

The PO told Kibblewhite made the valves for him before they started supplying them for the F2. He ordered his stuff in the US and Bikeside, Germany. The cam looks new, but engraved with WEB 63a 10-03. So it's from around 2003. It was a project that never got fully realized.
I paid €1250 / $1060 for the engine like listed above, including new clutch plates installed and new Honda carb insulators with it.
Excluding ignition and starter/alternator. It could have a better appearance though: needs a repaint and has a broken cooling fin.

[754]

Not bad if it's fresh..
 Remember forged 836 kit 500 +
 Boring to fit said kit            200 +
 Gaskets seals                      100.....
 800 and you only dealt with the cylinders... you are in great shape..

[Sam Green Racing]

The steal of the century, has he got any more, hahaha.

[Henkies]

I paid €1250 / $1060 for the engine like listed above, including new clutch plates installed and new Honda carb insulators with it.

Sorry, I should have divided the other way around! 1250 Euro is 1480 usd.

[Tintop]

Still a good deal.

[PeWe]

I used my K6 carbs with 836, ported head, cam, 4-1 which worked  OK.
Mikuni TMR32 work fine if you want to spend €€€. Full throttle with just a little twist, wheelie if you sneeze riding on 1:st gear taking off

I got mine from here: http://www.bikeside.de/shop/shop.php?bereich=Classic&aktion=anzeige_gross&ArtikelNr=59-2039
Ordered with filter adapters, KN oval pods to be added.
They were jetted:
Pilot 27.5 (Increased 1 step to 30)
Main 150  (132.5-137.5 depending on exhaust, 135 with rather open 4-1. I'll use 137.5 next year.
Needles 4:6 (reduced 2 steps based on dyno runs on cruising speed, now 2:nd notch of 6 from top)
Fuel screw 3/4 out from completely closed

They fit std CB750 K boots. F2 I do not know if the carbs have different spacing than K.

Mikuni RS34 cost less and have been used in several builds here with F2 heads.

[Henkies]

Mmm, valueble input PeWe, that's the next topic I'll be googling like an addict.
Too bad that many pictures on this forum aren't working anymore.

Isn't the RS34 too big for street use?
And on which bike were they? Gsx-750, and furthermore?

[PeWe]

Photobucket photos can be seen if you add an add-in in your browser
Here for chrome:
https://chrome.google.com/webstore/search/Photobucket%20Embedded%20Image%20Fix
Available for Firefox too. Search "Photobucket Embedded Image Fix"

[Henkies]

Photobucket photos can be seen if you add an add-in in your browser

Thanks!

[Tintop]

Photobucket photos can be seen if you add an add-in in your browser
Here for chrome:
https://chrome.google.com/webstore/search/Photobucket%20Embedded%20Image%20Fix
Available for Firefox too. Search "Photobucket Embedded Image Fix"

The Chrome fix worked for me.  That said, I have not tempted fate by accessing, or trying to load anything to my Photobucket albums.  Anything new will go to Flicker or...?

[PeWe]

I found the browser add-in for photobucket on the Open forum
http://forums.sohc4.net/index.php/topic,168102.msg1946279.html#msg1946279

I had missed vital photos in several threads and DIY on Internet in general. It should not be any problems since the add-ins can be found via the browsers gateway to add-ins and probably found to be OK.