Topic: Heavy Duty primary chains from M3...

[mystic_1]

If anything, this is the frustrating thing for anyone trying to build a CR750 replica - there's tons of knowledge out there, things have been tried over and over, BUT, there's just no repository for all of this information and those that have done the hard work seem very reluctant to share.

Isn't that part of what this place (sohc4.net) is for?

mystic_1

[kos]

Mark here from M3

I see the Ebay auction has people talking so let's clear up some odd notions going on here.  When we first started racing the CR750's I had 2-3 sets of the CR 750 Kit Racing primary chains in my parts selection. These were much superior to standard OEM chains and we never had  any breakage, but I used the F1 life-ing system to parts replacement. ie: replace parts at certain intervals that one determines via testing, to be within safe limits of the parts life before they break. Nice to do, when you have the extra parts and time to take the engine down. We finally ran out of parts and at the same time increased RWHP to just over 100HP. Yes, that is 100 RWHP from 762cc's. Our rider  had also honed his skills on the M3 CR750 and began "back'n the bike into the corners" ie: By going from 5th to 2nd directly and feathering in the clutch, causing the rear of the bike to "rear steer' into the corners, as it started to slide. Nice, exciting and put us miles ahead of any F750 rider/team so far. This combo had OEM chains coming thru the top of the engine cases from extreme "back loading" of the engine on a regular bassis. I started to look into the Hy Vo chain thing I had heard about for years, funny no one had ever done it. Some even said we should go with DOHC Honda 750 crank, as we could also change bore/stroke ratio. Wow, that sounds fun.... now we can try two things at same time and really screw up our winning combination. I set out to do the Hy Vo thing with CB750A crank and the GoldWing clutch dampener. Working directly with Morris Chains I found an engineer to work with and I had a source for my endless chains. Funny thing is...I was never able to find out where to get these chains from all those "experts" out there that were telling everyone, who would listen about the Hy Vo fix...because NO ONE ever did it!

To make the Hy Vo work, it needs two things, great tensioning system and an oil supply was what I was told. I made a special tensioning system and provided oil from rear galley at oil pressure switch area. This sytem did work and did extend time between changing out chains, but was not the most cost effective way to proced, so I have been looking for another way. Seems like we never broke any chains with Honda CR750 racing primary chains, when changed out on a carefuly timed schedule. ie: once a year, and yes we raced a lot for the first 3 years. (1997-1999)

Needless to say, I could never find any of those Honda CR750 chains...until now. Just last week I was contacted with an expert and now have 10 sets coming in first order. I have very detailed specs and comparison specs between OEM Honda and these new chains. At the same time as this happend, I was "schooled" on what breaks chains and it is NOT the acceleration under full throttle, but the loads that are impossed on the chain during deceleration! Fluctuating Tension is what the engineer told me..is what causes this. Also, when I started to look back on the engines (CB750/900/1100 & Kaw 500 twin) that used Hy Vo chains...they all drove the transmission via a "jack shaft" thus changing the chain speed and loads applied to the primary Hy Vo chain. As you now, the crank drives the tramission/clutch directly and at 10,500 RPM (sometimes 11,500) on the CB750 SOHC..that is too high for Hy Vo. Confirmed by my engineering contact at Morris, and knowing that I could not install a jackshaft drive system, I gave up on going that way. In fact, we stopped racing at the 100% level in 2001, due to the "racing became a job thing" with all the maintenance required to compete at that level.

Then within the last weeks, I found the direct replacement drive chains that are listed on e-bay now. I have 10 sets coming in first shipment and 4 are pre-sold. The price will be $450.00 per set,  and that is a deal... compared to spending dollars you need to to get Hy Vo right. Don't get me wrong, the Hy Vo can work, but the cost is very high and you will have to "life cycle" the chains on a regular bassis.

To sum this all up...we are a racing team and company that has travelled all over the world to race the best and are constantly striving to go faster, make more HP and win races. Doing this, we break parts, we improve them, we break other parts..on and on. I feel that these new chains are a very sound product and will work in any CB750 from street to roadrace.

Please any questions, contact me via web or phone.

Racing into the past,

Mark @ M3

[MRieck]

 Thanks Mark. I thought it was pretty common knowledge that snapping the throttle closed loaded up all chains more than the application of power. My dad told me this years ago (like 45) when I was skidding my bicycle. On the other hand he was a big engineer so I guess I was privy.  I still wonder about the stock tensioner spring and the extra weight associated with the new chains? Your thoughts if you read this. Thanks again.

[Terry in Australia]

G'Day Mark, Rex Wolfendon, (TRex Racing, Australia's premier CB750 based Post Classic race bike builder/racer) he's been using the hyvo chains on his race bikes since the early 1990's (maybe earlier, but that's when I first saw them) and his 1000cc+ engines are putting out 140+ BHP, so maybe he's perfected the chain tensioner problem? If you like I can find you Rex's phone number so you can ask him how he did it? Cheers, Terry.

[Terry in Australia]

eBay Username xref anyone?

http://forums.sohc4.net/index.php?topic=612.0

Sadly it's pretty much useless now Steve, as EBay "hide" all the other bidders user ID's, so you don't know who you're bidding against.

It really sucks, because it opens the door for crooked sellers to bid up their own stuff, even more than it did previously. Cheers, Terry.

[MRieck]

G'Day Mark, Rex Wolfendon, (TRex Racing, Australia's premier CB750 based Post Classic race bike builder/racer) he's been using the hyvo chains on his race bikes since the early 1990's (maybe earlier, but that's when I first saw them) and his 1000cc+ engines are putting out 140+ BHP, so maybe he's perfected the chain tensioner problem? If you like I can find you Rex's phone number so you can ask him how he did it? Cheers, Terry.

I'm very curious about this 140HP Terry. I'm assuming that is on an engine dyno. I feel very confident in that statement because 140 at the rear is over the top for NA.

[Terry in Australia]

G'Day Mike, that was the figure quoted in a magazine article I read about one of Rex's 1200cc bikes that they tested a few years ago. Unsure if it was engine or RW HP, but I would have said RW, as engine dyno's are pretty uncommon outside of factories.

Rex can certainly make them go, more than half of the Post Classic winning bikes here were built by Rex, including a couple that did well racing in the US, I believe? The "Phillip Island Classic" is on in a couple of weeks, so if I see Rex there, and he's not busy, I'll ask him for you. Cheers, Terry.

[MRieck]

G'Day Mike, that was the figure quoted in a magazine article I read about one of Rex's 1200cc bikes that they tested a few years ago. Unsure if it was engine or RW HP, but I would have said RW, as engine dyno's are pretty uncommon outside of factories.

Rex can certainly make them go, more than half of the Post Classic winning bikes here were built by Rex, including a couple that did well racing in the US, I believe? The "Phillip Island Classic" is on in a couple of weeks, so if I see Rex there, and he's not busy, I'll ask him for you. Cheers, Terry.

Rex has been around so long I'm sure he still uses an engine dyno. The big thing is you can't get enough valve into a SOHC to make that much HP to the rear UNLESS you run crazy compression (dragracing) WITH CB450 valves, + .200 deck etc, etc. I'm sure his figures are designer fuel etc as well as from the countersprocket. It took a lot of work for me to get a little over 150HP to the rear from an FJ1314. That's twice the valve area etc., etc.

[Jerry Rxman Griffin aka MuthaF'er]

Thanks for the info M3 Mark. Glad you're taking the interest to check in occasionally and be part of our insanity. Very enlightening. Hope you can also provide the info for the tensioner.

Now if we can just get the formula for the engines in your 100hp 762 and Rex's 140hp 1200 we'll all be happily breaking engines and buying new parts. 

[scondon]

G'Day Mike, that was the figure quoted in a magazine article I read about one of Rex's 1200cc bikes that they tested a few years ago. Unsure if it was engine or RW HP, but I would have said RW, as engine dyno's are pretty uncommon outside of factories.

Rex can certainly make them go, more than half of the Post Classic winning bikes here were built by Rex, including a couple that did well racing in the US, I believe? The "Phillip Island Classic" is on in a couple of weeks, so if I see Rex there, and he's not busy, I'll ask him for you. Cheers, Terry.

Rex has been around so long I'm sure he still uses an engine dyno. The big thing is you can't get enough valve into a SOHC to make that much HP to the rear UNLESS you run crazy compression (dragracing) WITH CB450 valves, + .200 deck etc, etc. I'm sure his figures are designer fuel etc as well as from the countersprocket. It took a lot of work for me to get a little over 150HP to the rear from an FJ1314. That's twice the valve area etc., etc.

      I was sent an article about Rex that talked a bit about the crazy stuff he does to his engines. I'll see if I can pull it off my dead computer. Real interesting stuff. I got it from a member here but can't remember who. Terry, bwaller, mrieck? cb1100 rods and crank fit into a SOHC engine with serious head and case work if I recall.

    All I really remember is the pics of his "sit up and beg" riding posture with just a number plate for a front fairing/windscreen.

[Terry in Australia]

I don't think it was me Sean, I've been hunting for the copy of AMCN (Australian Motor Cycle News) to find that article by Alan Cathcart (Sir Alan, the Marquis De Cathcart) but I think that damn woman threw it out!

But yeah, Rex is pretty amazing, I've seen a head he built where he welded up the ports, combustion chambers and the valve guide holes, and virtually re-manufactured it with massive ports and different valve angles to allow much bigger valves, and as you mentioned, with the CB1100F crank, these bored and stroked beasts still look like CB750 engines, but that's where the similarity ends, ha ha! Cheers, Terry.    

[Retro Rocket]

Yep Rex sure knows how to build a honda/4, his feats are well known in racing circles in Australia.


Here's 2 of his race bikes.
These things make Kawasaki 900's look like girls bikes....


Mick

[voxonda]

Since I started with the 750 say 34 years ago I always found the 'sound' of the primaries very offending. Not being able to do anything about the two seperate chains I focussed on the tensioner. I, also, feld the lack of positive tension was the problem. I 'solved'(?) it my way, well had never any problems with it, though am not as skilled a rider as Adam Popp, to say the least.




It is quite simple, but have never encountered any issue's with the chains afterwards. Big problem still is that you try to tension two seperate chains with one tensioner. Chains will never stretch evenly!

Cheers, Rob

[MCRider]

Since I started with the 750 say 34 years ago I always found the 'sound' of the primaries very offending. Not being able to do anything about the two seperate chains I focussed on the tensioner. I, also, feld the lack of positive tension was the problem. I 'solved'(?) it my way, well had never any problems with it, though am not as skilled a rider as Adam Popp, to say the least.




It is quite simple, but have never encountered any issue's with the chains afterwards. Big problem still is that you try to tension two seperate chains with one tensioner. Chains will never stretch evenly!

Cheers, Rob

More detail please! It looks like a plate you put under the tensioner. But it also looks like the angle of the tensioner has been changed... with more spring?

[bwaller]

Sean, I must have sent you that article and I probably still have it. I will try to dig it out and scan it if the guys are interested.

[voxonda]

More detail please! It looks like a plate you put under the tensioner. But it also looks like the angle of the tensioner has been changed... with more spring?

Hi MC,

The 3 m/m (about 1/8")plate sits inside the tensioner under the spring and is hold in place by the mountingbolt of the tensioner. In that way the angle changes.

Cheers, Rob

[NitroHunter]

I too have a similar plate under the tensioner mount base. I felt there was a need for more tensioner spring pre-load and this was an easy fix. It seemed to reduce the noise under deceleration conditions, especially with my high compression motors (one had 240 psi cranking psi ). Having a welded clutch hub certainly didn't help, and the lack of 'cush' in the drive train must have been playing hell with the primary chains. Maybe I got lucky none broke, I did replace several when I noticed they were getting sticky, though nowhere near as bad as some cam chains got. Of course once I started using the heavy duty cam chains I saw no more problems there, but was never able to find a similar primary chain set.
Bwaller, what article are you referring to? I'd love to see it.
NitroHunter

[MCRider]

More detail please! It looks like a plate you put under the tensioner. But it also looks like the angle of the tensioner has been changed... with more spring?

Hi MC,

The 3 m/m (about 1/8")plate sits inside the tensioner under the spring and is hold in place by the mountingbolt of the tensioner. In that way the angle changes.

Cheers, Rob

Oh! That's cool. I thought the plate was going underneath the tensioner between it and the cases, and that you had done something else to the spring besides.

But what you've done makes perfect sense. I think I'll go a little more conservative with half that pre-load.

Thanks!

[MRieck]

G'Day Mike, that was the figure quoted in a magazine article I read about one of Rex's 1200cc bikes that they tested a few years ago. Unsure if it was engine or RW HP, but I would have said RW, as engine dyno's are pretty uncommon outside of factories.

Rex can certainly make them go, more than half of the Post Classic winning bikes here were built by Rex, including a couple that did well racing in the US, I believe? The "Phillip Island Classic" is on in a couple of weeks, so if I see Rex there, and he's not busy, I'll ask him for you. Cheers, Terry.

Thanks Terry.....I'd appreciate that.

[HondaMan]

Hmmm...this feels like someone threw down the gauntlet...

Diamond makes the strongest chains in existence. Eveyone in the world copies the innovations Diamond brings out. I think I'll contact their Engineering group this week.

The CB750 unevely loads these two chains. Any of you who have torn one down has discovered that one chain is longer than the other. Here's a clue: it's always the same chain, if the teardown is the first daylight in an OEM engine. The reasons: the bearing structure and lack or parallelism between the shafts, due to the use of certain cheap-metal transmission bearings, and a little bit of shaft twist from the torque, in opposite directions between the crank and transmission. Stronger chains will help, but so will better bearings. Both together will put more HP on the ground in the end. This was always part of my "blueprinting" scheme for stock racers, and one of those places where the (then) superior Timken bearings played a part. Now, apparently, Timken is out of the ball bearing business. 

Last time I looked, Diamond had a chain that is strong enough that one chain could carry the load that both chains used to, and could run without the oil bath method...together, two will do nicely! Maybe this could remove the "limited production" status?

[voxonda]

Hi Mark,

Can hardly wait on the outcome! Please, keep us informed!

Thanks mate!

[HondaMan]

The big thing is you can't get enough valve into a SOHC to make that much HP to the rear UNLESS you run crazy compression (dragracing) WITH CB450 valves, + .200 deck etc, etc. I'm sure his figures are designer fuel etc as well as from the countersprocket. It took a lot of work for me to get a little over 150HP to the rear from an FJ1314. That's twice the valve area etc., etc.

That's what I thought, too...breathing is everything for these engines. 

[kos]

Daytona....1999 We had just brought out our newest version of the M3 CR750 to Daytona. This is the one that had new OEM chains in it, as we had run out of CR racing chains and it was running our new and improved F2 head 35mm intakes and 30mm exhaust valves out of Ti. Just after setting the Classic Bike Daytona track record of 155.556 mph the chains came out of the top of the cases. Guess who was the first one over to try help us with the rebuild of the engine...Rex from down under. He was there with the Trinder Bros and they were taking on Daytona for the first time, abeit the AHRMA rules...gasoline only and this was causing them, no end of trouble as all they were use to running ALCOHOL! Rex had very litle experience with gasoline and small cc engines. AHRMA rules 762 max cc in F750.

We got on well and have stayed in contact for a few years, but I have lost touch, but would love to get a phone number or e-mails address from anyone who might know of it?

Yes, I know that he makes a special nylon block of his own design for the tensioning of the Hy Vo chains, but keeps it close to himself, as he does not want to let go of all of his hard earned victorys.  he also, knows about changing out the chains in order to prevent chain failures, but his tensioner would be a great addition to the Hy Vo equation.

As for his HP 1200cc's on achohol...140 at crank is not unrealistic, and he has the benefit of running that big 1200cc engine at much lower RPM and that helps with the Hy Vo chains living longer. 8000-8500 RPM is a lot beter than 10,500-11,000.

Also, I have worked with a guy from Indiana that builds sawed off (ie: no gear box) CB750 SOHC engines on alcohol that run in TQ midget cars. He runs at 836cc (12.5/1 compression) and dynos at crank 118-120 HP. He has a comination of 71mm bore with 52.8mm stroke that bhe was going to try, but I never heard how far he went with this, but I'll check on it and come back if there are any details.


Mark @ M3

[HondaMan]

Also, I have worked with a guy from Indiana that builds sawed off (ie: no gear box) CB750 SOHC engines on alcohol that run in TQ midget cars. He runs at 836cc (12.5/1 compression) and dynos at crank 118-120 HP. He has a comination of 71mm bore with 52.8mm stroke that bhe was going to try, but I never heard how far he went with this, but I'll check on it and come back if there are any details.
Mark @ M3

Mark:
Is this an older guy (like me) with a backburn (maybe still) and bald top, named "Jeff" or "Jack" (or something with a "J"), who was also doing this with these engines in the early 1970s? If so, I know him, but he was in southern Illinois then. I helped build a 16,000 RPM version of one back then for a midget car.

[754]

if an  street 836cc on here cranks 93 HP at the rear wheel, should not a 1080 be capable of around 120 ish?

 And what if you ran a blower?

 Are you guys saying they allow roadracing on Alcohol down under?

--------------------------------------------------------------------------------------

Just an observation I made a few decades ago, I have not been inside these engines much, for a long time.

The first time I looked at the primary chains installed with cases split, I notice one tight, one slack  . Now I think I carefully inspected the sprockets and thought it seemed the sprockets were slightly out of phase (this can easily be checked with a rod or drill shank the size of the roller) and had come to the conclusion the the "Clevel Bastalds" in engineering HAD THOUGHT OF everything..

at any rate , I would at least inspect that aspect.