Topic: Connecting Rods

[72cafe]

So I've picked up my first CB750 ever. I paid about $275 for it and it runs pretty well, but it has about 35000 miles on it. I am gonig to rebuild the entire engine to (nearly) new. The one question I have right now is this;

Is there a connecting rod on the market that is better than stock but not as pricey as Carrillos? I am not planning to make this bike a drag bike or anything, so I don't want to drop nearly $1000 on the rods alone. I am planning to bore it up to 836, but I don't see how that would call for the highest end rods on the market.

[MRieck]

 Falicon makes rods for the CB but they list for 225.00 each ( I can get them for a little less).. They are their "Knife" design. I run their older 2 piece steel rod with updated ARP bolts in my 915cc. You can have the OEM rods polished. balanced and shot peened too which will run you 60.00 to 70.00 per rod. The real weak part in the OEM rod are the bolts. If you could source out some ARP's and polish etc you'd have a good rod for 836cc. To be honest for the extra 25.00 a rod I'd get Carrillo's if I were in the market for rods. The Falicons are more than strong enough for anything you can put in the CB BUT Carrillo's are the best....period. Expect an 8 to 10 week wait for Carrillo's. Falicon can get a set to you in about 7 to 10 days(in general). I hope this helps.

[MRieck]

.....at the least F3 rod bolts.

[mikeb4]

Here is a set I just saw on eBay .... no relation to the seller but they look cool and are new & cheap - http://cgi.ebay.com/ebaymotors/ALUMINUM-FORGED-CONNECTING-ROD-KIT-FOR-HONDA-CB750-NEW_W0QQcmdZViewItemQQcategoryZ10066QQitemZ4584140706QQrdZ1QQsspagenameZWDVW

[cd811]

a friend of mine GAVE me a set a set of rods. he said they were some kind of "racing, high performance" rods. they "feel" light and strong. now you know as much about them as me. if they interest ya, let me know.

[Bodi]

A trusted engine builder told me to avoid aluminum alloy rods. He had in his junk pile an exploded 750 motor with the stub of one poking out the side and at least one set of stretched rods that had destroyed valves to show me why he disliked them.
Maybe they're good and he's had bad luck? I don't know, but I know of no production or racing engine that has aluminum rods.
The advice I got was that if I couldn't afford Carillo or Falicon rods then the stock ones would be way better than alloy, stock rods can be reworked a bit to lighten and balance them before shotpeening.

[oldbiker]

Hi Bodi, the Triumph twins of the 1960-70's all had alloy connecting rods. I adapted one to run in my 250 single clinder Triumph racer but of course revs only ran to about 7000 then. Properly engineered, they are OK.

[MRieck]

Hi Bodi, the Triumph twins of the 1960-70's all had alloy connecting rods. I adapted one to run in my 250 single clinder Triumph racer but of course revs only ran to about 7000 then. Properly engineered, they are OK.

That is a fact. They used steel big end caps though. All aluminum rods have a  finite service life and they stretch quite a bit. I have used the old RC Golden Rods as well as MTC's with no problems in other peoples engines. I prefer a good steel rod, or better yet titanium rod, in my personal engines. Carrillo's are often lighter than the OEM rod too.

[dusterdude]

true,an aluminum rod is not a put in and forget it rod.they must be maintained quite often.

[bryanj]

Yes oldtimer the Triumphs did have alloy rods and if you go back to the 500 there were no shells just whitemetal on the steel cap with the alloy rod running on the crankpin. Also the power output on the Triumph is WAY bellow that on the standard Honda, never mind a tuned one. so they aint stressed anywhere near

[joeb]

You can give this a try they have some pretty interesting stuff. http://www.cyclexchange.net/  look under engine parts.

[MRieck]

You can give this a try they have some pretty interesting stuff. http://www.cyclexchange.net/  look under engine parts.

I wouldn't pay 10.00 for those steel rods labeled CR750. They are total junk. Don't ask me how I know that.

[Sam Green Racing]

How do you know that ??   

[MRieck]

How do you know that ??   

Because you're asking the question Sam I'll answer. I bought a set on ebay a while back and when I got them I could see how #$%*ty they were. One of the big end caps had 2 bearing holding slots cut into it! The big end on 2 rods had been initially made to big so when they honed them(kinda of) the raw casting was visible around the outside edges. The pieces were #$%*....plain and simple and I spent over 150.00 to purchase them. I've thought about making some wierd type of lamp out of them but every time I look at them I get sick. I packed them away so deep my kids won't find after I'm dead.

[Sam Green Racing]

I was only jokeing Mike but seeing you took the trouble to answer, can you not turn them into an ebay sucks sign with all your skills?

[MRieck]

I was only jokeing Mike but seeing you took the trouble to answer, can you not turn them into an ebay sucks sign with all your skills?

Now there is an idea Sam!!

[Dragman836]

Hi Bodi, the Triumph twins of the 1960-70's all had alloy connecting rods. I adapted one to run in my 250 single clinder Triumph racer but of course revs only ran to about 7000 then. Properly engineered, they are OK.

That is a fact. They used steel big end caps though. All aluminum rods have a  finite service life and they stretch quite a bit. I have used the old RC Golden Rods as well as MTC's with no problems in other peoples engines. I prefer a good steel rod, or better yet titanium rod, in my personal engines. Carrillo's are often lighter than the OEM rod too.

I got a set of alum. MTC rods for $100 , polished them and I was wondering if cryrogenicly treating these would greatly improve their life span and dependability and how much and who would do this?

[Big Jay]

A trusted engine builder told me to avoid aluminum alloy rods. He had in his junk pile an exploded 750 motor with the stub of one poking out the side and at least one set of stretched rods that had destroyed valves to show me why he disliked them.
Maybe they're good and he's had bad luck? I don't know, but I know of no production or racing engine that has aluminum rods.
The advice I got was that if I couldn't afford Carillo or Falicon rods then the stock ones would be way better than alloy, stock rods can be reworked a bit to lighten and balance them before shotpeening.

All top fuel motorcycles, the fastest in the world, use aluminum rods.

Jay

[cafe75-550]

Yes oldtimer the Triumphs did have alloy rods and if you go back to the 500 there were no shells just whitemetal on the steel cap with the alloy rod running on the crankpin. Also the power output on the Triumph is WAY bellow that on the standard Honda, never mind a tuned one. so they aint stressed anywhere near

Actually, the rods for the 650 Bonnie's are stressed more, considering that they put out 50 bhp and only have two cylinders to divide the power, while the 750 is at  75 bhp but with 4 cylinders, so the rods on the 650 are carrying 25bhp vs 18.75 .... Not to mention the longer stroke. And that doesn't get into the Triumph 750's...

[scondon]

 Back to the original post, if you're planning on building a engine that will primarily be used for city/weekend riding, and not the race track, then I think the stock rods will suffice. I've got a 836 that I ride daily, usually in the 6000-9000rpm range, and it is holding up well after a year of riding. I recently had it Dyno'd and ran it up to 10,000rpm and nothing exploded, in fact it sounded like it could take a little more. Completely refurbished head w/heavy duty springs,of course.

  The rods I'm using are the F3 rods that Mike mentioned and they look identical to earlier rods except for the longer bolts so I don't see why not just order the bolts/nuts and put them in your rods. I had Mike shotpeen,balance, and polish another set that is going in the engine I'm currently putting together. For more info check this thread:

http://www.sohc4.us/forums/index.php?topic=14934.0

  It's easy enough to start throwing a lot of money for "performance this" and "performance that" when you build an overbore engine. Headwork,pistons,boring,crank and rod bearings,primary chains,cam chain,cam,maybe some better carbs and pods to increase the top end, etc... Before you know it you're at $2500 and that extra grand for some killer rods seems like a good deal to protect all the money invested so far. But if you're not planning on racing the bike and holding the rpm's above 9500 for long extended periods then,in my opinion, you probably don't need them.

   Again, this is just my opinion and not some bit of fact backed up by years of "high powered" experience

[sparty]

  It's easy enough to start throwing a lot of money for "performance this" and "performance that" when you build an overbore engine. Headwork,pistons,boring,crank and rod bearings,primary chains,cam chain,cam,maybe some better carbs and pods to increase the top end, etc... Before you know it you're at $2500 and that extra grand for some killer rods seems like a good deal to protect all the money invested so far.

Tell me about it.  The $$$ signs add up really quickly.  But my MRieck engine will be well worth it.  The way I look at it, I could be spending the money on useless stuff or a new $10K bike.  I figure for just under $6K I’ll have a killer motor and a hell of a good time.

Sparty

[kghost]

The Right combination goes a long way to making good power.

As does absolute precision on assembly.

I have a pedantic streak a mile long. Break out the burette and lets CC them combusion chambers 

All the spark pugs pointing the same way?

Cam degreed to perfection?

All the valve spring tensions the same?

Hells bells is the timing cam and advance plate right?

I swear I could wear an engine out assembling, checking, disassembling, rechecking.....

Can't stand reassembling with out all new bearings and seals. Even the tranny ones.

I think I spent more time assembling my engine the all the rest of the bike. 

[sparty]

The Right combination goes a long way to making good power.

As does absolute precision on assembly.

I have a pedantic streak a mile long. Break out the burette and lets CC them combusion chambers 

All the spark pugs pointing the same way?

Cam degreed to perfection?

All the valve spring tensions the same?

Hells bells is the timing cam and advance plate right?

I swear I could wear an engine out assembling, checking, disassembling, rechecking.....

Can't stand reassembling with out all new bearings and seals. Even the tranny ones.

I think I spent more time assembling my engine the all the rest of the bike. 

Better safe than sorry, plus it is fun getting greasy.  I feel the same way, I spend double or triple the time on simple projects because I want them to be perfect and problem free.  When I tackled my front brakes, I went overkill but i am glad that I did, they are squeel free and stop on a dime (well, a really really big dime), you know CB brakes

Sparty

[kghost]

Ever notice that the smaller the person the worse the CB brakes are? 

I also believe there is a direct corellation between years spent with drums.........

[Dragman836]

I have about 10 sets of stock cast rods , what would ID the F3 rods vs k or other rods? Also I have a shot peen machine accross the street ( Pangborn ) I can get access to, so how long do the rods need to be blasted and how  do I protect the bearing area and piston pin hole?