Author Topic: SOHC Engineering (Read 9152 times)

Whaleman · « **on:** November 24, 2009, 05:12:13 PM »

I should begin with the fact I love the design, engineering and looks of the SOHC 750. I am in the process of rebuilding my first DOHC 750 for a friend. His engine threw a rod at over 100MPH because of a bad oil pump pickup design and weak pressure relief spring. I have had to spend hours at the DOHC forum site to learn of all the problems and how to fix them. His engine was unrepairable and I am repairing an ebay engine. I believe Honda engineering on the DOHC was not as good as our older SOHC. My brother, who is the owner of the company I work for, has put in a quarter million down payment on a Honda Jet Airplane due out in 2011 or so. It will sell for 3.5 million+. He did not really plan to buy one but he felt his down payment got him a place in line and he will be able to sell for a profit to someone else ( or he buys if economy turns around a little). Just last week they sent out a hardcover book to all the depositors about the history of American Honda. It is a super amazing read. I will see if I can scan and post. The beginning of Honda was not meant to be the Cub but the real bikes burnt up and Honda pulled them all back to Japan and all they had left was the Cubs. The file will be huge but the photos and interviews are great. Lots of SOHC references and photos. A little teaser.... When the man was chosen to start American Honda came over and he was given a budget. He bought a building instead of renting and only had 20K left to start American Honda. It shows photos of the one Secretary and the office. More later Dan

Old Scrambler · « **Reply #1 on:** November 24, 2009, 05:46:31 PM »

Looking forward to the read.

Sochiro Honda got started by selling his replacement piston-ring factory to Toyota because the rings were better than the stock items.

wannabridin · « **Reply #2 on:** November 24, 2009, 05:57:00 PM »

i would most certainly be down for that read!! even if you were willing to put it on a cd, i'd be down for sending you some money to cover the cd and shipping

Simpson · « **Reply #3 on:** November 24, 2009, 06:51:51 PM »

This should be good!

Can't wait...

BobbyR · « **Reply #4 on:** November 24, 2009, 06:52:10 PM »

Rumor has it the SOHC was supposed to be retired quite a few years before 1979. They stayed with the SOHC till and kept making improvements until 1978. In 1979 I guess they either figured they had the problems licked or took a shot to stay competitive. Very few DOHCs out there still running and look at all these SOHCs

Terry in Australia · « **Reply #5 on:** November 24, 2009, 07:14:41 PM »

The DOHC 750's, 900's and 1100's (F models, the "R" was an entirely different engine, and a beauty) were rushed out in an attempt to stay competitive with the other Jap manufacturers, and had lots of problems, but the main reason that there are so few left on the road is that they were a sales flop and not sold in the same numbers as the mighty SOHC CB750, (500,000 units sold) so Honda then rushed out the first "VF" series bikes, which, once again, were dogs, plagued with all sorts of problems. The smaller "VT" range was rubbish too, the CBX550 DOHC4 was a shocker, so it wasn't until the first "VFR" and "CBR" models emerged in the mid eighties did Honda begin to claw back it's reputation for quality workmanship. Cheers, Terry.

754 · « **Reply #6 on:** November 24, 2009, 07:24:41 PM »

single stick 4 will rule 4ever....

HB-1fan · « **Reply #7 on:** November 24, 2009, 07:34:27 PM »

Hey whaleman, some food for thought on parts. While at the Valdosta drag races, I went over to the MTC trailer and was looking through some NOS parts they were trying to unload. There in a box was a bunch of new sets of DOHC 750 rods still packaged. They wanted $50.00 for a set of 4. There was approx. 6 sets!!!! Go to their website and inquire!!
Don't know if they are usable for any sohc engines. Maybe someone else can throw out the specs for them.
I to will like to read it when you get it in writing!!

Hopes it helps!!

HB

Magpie · « **Reply #8 on:** November 24, 2009, 07:50:46 PM »

A good read about the Honda story is "Honda:The man and His Machines" by Sol Sanders.
Cliff.

mick7504 · « **Reply #9 on:** November 24, 2009, 07:51:58 PM »

Quote from: HB-1fan on November 24, 2009, 07:34:27 PM

Hey whaleman, some food for thought on parts. While at the Valdosta drag races, I went over to the MTC trailer and was looking through some NOS parts they were trying to unload. There in a box was a bunch of new sets of DOHC 750 rods still packaged. They wanted $50.00 for a set of 4. There was approx. 6 sets!!!! Go to their website and inquire!!
Don't know if they are usable for any sohc engines. Maybe someone else can throw out the specs for them.
I to will like to read it when you get it in writing!!

Hopes it helps!!

HB

The 750 & 900 DOHC rods are the same specs (Big End & Small End) as the 750 SOHC rods.
The 750 DOHC rods are anout 1.5mm (.060") shorter and the 900 DOHC rods are about 1.5mm (.060") longer.
I've done a couple of rebuilds with 900 DOHC rods in a 750 SOHC and put a .060" aluminium spacer under the cylinder to compensate.
Seems to work fine and is a cheap alternative for stronger rods.
Here is some more info on Axl's site about this.
http://www.satanicmechanic.org/conrods.shtml

camelman · « **Reply #10 on:** November 28, 2009, 12:27:17 AM »

Just remember. If it weren't for Harley Davidson, we would never have been blessed with the SOHC4s. It would have been DOHCs all the way.

Camelman

mick7504 · « **Reply #11 on:** November 28, 2009, 01:29:08 AM »

Quote from: Whaleman on November 24, 2009, 05:12:13 PM

I should begin with the fact I love the design, engineering and looks of the SOHC 750. I am in the process of rebuilding my first DOHC 750 for a friend. His engine threw a rod at over 100MPH because of a bad oil pump pickup design and weak pressure relief spring. I have had to spend hours at the DOHC forum site to learn of all the problems and how to fix them. His engine was unrepairable and I am repairing an ebay engine. I believe Honda engineering on the DOHC was not as good as our older SOHC. My brother, who is the owner of the company I work for, has put in a quarter million down payment on a Honda Jet Airplane due out in 2011 or so. It will sell for 3.5 million+. He did not really plan to buy one but he felt his down payment got him a place in line and he will be able to sell for a profit to someone else ( or he buys if economy turns around a little). Just last week they sent out a hardcover book to all the depositors about the history of American Honda. It is a super amazing read. I will see if I can scan and post. The beginning of Honda was not meant to be the Cub but the real bikes burnt up and Honda pulled them all back to Japan and all they had left was the Cubs. The file will be huge but the photos and interviews are great. Lots of SOHC references and photos. A little teaser.... When the man was chosen to start American Honda came over and he was given a budget. He bought a building instead of renting and only had 20K left to start American Honda. It shows photos of the one Secretary and the office. More later Dan

Dan, I don't know if we have the same book but I have just been reading one titled Honda - edited by Mick Woollett.
It is an excellent read starting with the humble beginnings of Soichiro Honda and the progression from there.
Really enjoyed reading it.
One that got me curious was if there was any connection between Honda's ART workshop and the ART piston manufacturing Company. Maybe just a coincidence.
A picture from around 1946 below.

Here are a couple on ebay if anyone is interested.
http://cgi.ebay.co.uk/HONDA---MICK-WOOLLETT---1983_W0QQitemZ250520155009QQcmdZViewItemQQimsxq20091126?IMSfp=TL091126157007r17601

http://cgi.ebay.com.au/HONDA-Edited-by-Mick-Woollett-History-of-the-company_W0QQitemZ380182218170QQcategoryZ1132QQcmdZViewItemQQ_trksidZp4340.m263QQ_trkparmsZalgo%3DSI%26its%3DI%26itu%3DUCI%26otn%3D10%26ps%3D63
Some used copies here at Amazon as well.
http://www.amazon.com/Honda-Mick-Woollett/dp/0600349942

754 · « **Reply #12 on:** November 28, 2009, 08:34:20 AM »

Camelman, how do you figure that..

vanillagorilla · « **Reply #13 on:** November 28, 2009, 06:46:25 PM »

Quote from: 754 on November 28, 2009, 08:34:20 AM

Camelman, how do you figure that..

I can't make sense of that either... Enlighten us! Most smaller displacement HDs had multiple cams, the big twins(knucks, pans, shovels, etc) were single cam, until the twin cam 88 came out in 99... Funny thing about HDs, what we get out of a 45" motor, they barely get out of an 88 incher!!! Got to love those old tractors(BTW I am a certified HD tech, so I can talk bad about 'em if I want)!

754 · « **Reply #14 on:** November 28, 2009, 07:59:57 PM »

Maybe we should compare it to an XR 750

I want to see someone with a SOHC Honda, doesnt matter how big, beat Burt Munro's record.. what he did with a 1000cc pushrod engine, which started out as a 600cc 60mph bike..

vanillagorilla · « **Reply #15 on:** November 28, 2009, 08:24:16 PM »

Well Burt Munro's story is more of a testament to him than the bike. Makes you wonder though... Streamliner body, turbo, really tall gearing... Wonder how fast a cb750 can go... Bet the 750 could do it with a 3/4 the displacement!

754 · « **Reply #16 on:** November 28, 2009, 08:30:58 PM »

Williams out of Windsor Ontario has done over 200 mph on 500cc Honda, but it is a DOHC, a sleeved down CBR motor.

Burts bike, I believe had better aero than many other bike streamliners, not all of them. But very impressive for what he had to work with.

camelman · « **Reply #17 on:** November 28, 2009, 08:46:43 PM »

When Honda introduced the DOHC CB450 in the 60s, it became an immediate success at the track. It was so successful, and dominated the HD and British bikes so well, that Harley used its political muscle to ban DOHC engines in AMA competition. Honda had to respond with a new engine design, which added more support to the SOHC engine series that we have all come to know and love. If it weren't for this rule, then Honda would have continued to develop the DOHC in the 60s, and our lovely SOHC power plants might never have had a chance to develop.

Harley later followed up with another rule in the AMA allowing them an additional 250cc because of their archaic engine design. It sure is funny how HD "evened" the playing field. Most manufacturers tried to improve their products. HD tried to hold everyone else back.

Camelman

vanillagorilla · « **Reply #18 on:** November 28, 2009, 08:53:36 PM »

Ohhh ok. I wasn't thinking about that side of HD. They do like to stack the deck in their favor don't they!!! Flat tracking is almost soley HD, as is hill climbing... They have their own drag racing association. Damn dirty cheaters. I just had to set a HD buddy of mine straight, actually. Its funny how they still feel like they are riding the better bikes. He at least is on a v rod though...

von_Wanderlust · « **Reply #19 on:** November 28, 2009, 09:22:27 PM »

Quote from: camelman on November 28, 2009, 08:46:43 PM

Harley used its political muscle...

Really? Interesting, and to be honest, not surprising. I bet it was done in conjunction with a nice little marketing campaign for 'grown at home' bikes. Mobilising the public for their own personal gain.

I'm still p!ssed that they (i.e. the local manufacturers) did a similar thing with the Nissan GTR in our Bathurst car race.

Long live the GTR. (Insert raised fist emoticon here. I choose a raised fist as it seems that the local manufacturers are the oppressors of technological advancement.)

vanillagorilla · « **Reply #20 on:** November 29, 2009, 06:48:44 AM »

Quote from: von_Wanderlust on November 28, 2009, 09:22:27 PM

Quote from: camelman on November 28, 2009, 08:46:43 PM
Harley used its political muscle...

Really? Interesting, and to be honest, not surprising. I bet it was done in conjunction with a nice little marketing campaign for 'grown at home' bikes. Mobilising the public for their own personal gain.

I'm still p!ssed that they (i.e. the local manufacturers) did a similar thing with the Nissan GTR in our Bathurst car race.

Long live the GTR. (Insert raised fist emoticon here. I choose a raised fist as it seems that the local manufacturers are the oppressors of technological advancement.)

How did they screw over the mighty GT-R, mate? THAT is some kind of car! My boss has one. Still pestering him for a ride along. We'll see... Doubt it, he is kind of a douche.

Sam Green Racing · « **Reply #21 on:** November 29, 2009, 08:05:04 AM »

Quote from: 754 on November 28, 2009, 07:59:57 PM

Maybe we should compare it to an XR 750

I want to see someone with a SOHC Honda, doesnt matter how big, beat Burt Munro's record.. what he did with a 1000cc pushrod engine, which started out as a 600cc 60mph bike..

Frank, back in the early 80s I think, an Irish guy nearly did it.
He had several attempts at the British record and I think he may still hold the Irish LSR to this day.
The bike was a SOHC, don't remember much about it but it was a strong contender and still looked like a modded road bike.
I've searched for info in the past for this bike and drew a blank, it ran close to 200mph from what I can remember on a public road in Cork.

Sam.

mick7504 · « **Reply #22 on:** November 29, 2009, 05:33:41 PM »

Sam, Was this guys name Danny Keany?
http://www.independent.ie/unsorted/features/danny-keanys-yamaha-tz750-133056.html

Terry in Australia · « **Reply #23 on:** November 29, 2009, 07:31:52 PM »

Was the Yamaha TZ750 a SOHC, or DOHC? I saw one once, geez it was blowing smoke mate, I reckon it must have busted an oil ring?

mick7504 · « **Reply #24 on:** November 29, 2009, 07:45:54 PM »

Terry
I think they are a 130 mile an hour water cooled two stroke.
That would explain the smoke.

Mick

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Author Topic: SOHC Engineering (Read 9152 times)