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Author Topic: turbo charged 71 Honda 750  (Read 7525 times)

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the glass man

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turbo charged 71 Honda 750
« on: July 19, 2009, 06:52:23 am »
I have a Turbocharged 71 Honda 750,
      I live in the Florida Keys and the egine gets pretty hot when driving in towns, it has an added oil cooler. Can I get it to run cooler? The engine is worked over with Yoshimier equipment. Can anyone out there give me some advice.---Tony the glassman

Offline themotoworks

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Re: turbo charged 71 Honda 750
« Reply #1 on: July 19, 2009, 06:53:16 am »
intercooler for the turbo?
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Offline KCRSXTypeS

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Re: turbo charged 71 Honda 750
« Reply #2 on: August 03, 2009, 09:44:46 am »
I agree on the intercooler but maybe also utilize an intercooler sprayer.  Really easy to build.

Offline PxTx

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Re: turbo charged 71 Honda 750
« Reply #3 on: August 03, 2009, 10:24:46 am »
Do you have the E85 fuel down there?  I have seen some great tunes with E85 and turbo cars where the intake actually develops frost and the EGT are on par with gasoline.  E85 is just over $2 in PA, but there are only a few stations near me.  Range is not as good as gasoline, but could be a nice solution fo you.  What carbs are you running?

Offline scartail

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Re: turbo charged 71 Honda 750
« Reply #4 on: August 03, 2009, 11:15:41 am »
I think the guy is heating up "when driving in towns".

I think the intercooler will help keep intake temp down when he is beating on it (and alot of air flowing over the intercooler). For stop and go driving, it may not be the best bang.

Our air-cooled bikes have it bad. To bad we don't have radiator kits for our bikes.

Anyway, I'm just throwing an idea out there.
Can you put a fan on the oil cooler? Bigger oil cooler with fan? What about oil type/weight?

I live up in west palm beach, and it is getting too hot to ride during the days.
« Last Edit: August 03, 2009, 11:19:37 am by scartail »
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Offline NitroHunter

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Re: turbo charged 71 Honda 750
« Reply #5 on: August 03, 2009, 08:48:20 pm »
Welcome to the forum, my turbo brother!
I'll go out on a limb here  ::) and guess we're talking about either an ATP or Mr. Turbo kit.

Since these both are draw through systems - the turbo sucks through the carb - the use of an intercooler is virtually impossible, as the atomized fuel would fall out of suspension and simply puddle in the heat exchanger.
In town the motor sees little load - and it's load (heat) that spools up the turbo. Boost = Intake manifold heat, but nowhere near as much as the motor makes just loping through traffic.

Some of the little things that can help: cooler spark plug heat range during this warm weather, verifying ignition timing and spark advancer working correctly, idle / mixture  not lean, and (most important to me): Is your fuel pump/regulator/filter/petcock in great condition?
All these things being good, I simply had to accept that my turbo bike runs hot. Run good 20w-50 wt. oil, and change it often. My bike would constantly see oil tank temps of 275+...

Glassman, we need to see some pics of your machine!

 
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Offline Zaipai

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Re: turbo charged 71 Honda 750
« Reply #6 on: August 03, 2009, 08:59:33 pm »
Glassman, we need to see some pics of your machine!

Agreed! Don't see too many turbos...
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Offline JLeather

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Re: turbo charged 71 Honda 750
« Reply #7 on: August 11, 2009, 06:34:24 am »
Not only is an intercooler ineefective for a draw-thru, but it's unsafe.  I've heard that the atomized fuel in the intercooler can ignite from a backfire and actually blow the intercooler apart (nasty shrapnel, etc).  Bottom line is no intercooler for a draw-thru.

I for one would be thrilled to hear what's been done to the motor and how it rides on the street.  I'm still putting together a mostly-streetable turbo engine from an ATP kit as well and I'd like to know how the fuel consumption is, what carb you're running, what fuel pump/regulator, how it goes and stops, what ignition system and timing is on the bike, etc.

I'm 99% sure that's an ATP kit, and it's an early kit because it has the log-style manifold.  I've talked to Terry at Mr Turbo and he told me they didn't actually offer a CB750 "kit".  They did one for the 550, and they sold parts, but that setup there is likely ATP.

The ATP kit for the street was allegedly "bolt on and go".  I've got a few mags that talk about it and supposedly you didn't change anything, not even the ignition system or timing, for up to 4-5 pounds of boost.

The oil-cooler is definitely a good start.  If you wanna go through the trouble the best way to cool the bike would be water/meth injection.  There are some fairly small setups for the tuner crowd with integrated pumps and all.  It's a bit of extra plumbing, but not too bad since it's a single manifold anyway.  Might be more current draw than the CB is good for though.  I looked into them, but decided ultimately that it was just too much extra crap to carry along.

Another way to keep temps a bit better is more oil capacity.  A larger oil tank, or secondary reserve tank.  There was also back in the 70's a deeper pan for the 750's (not an auto pan, they don't fit the K's) that also had more fins on the inside.  That would help.  I'd imagine you can have a shop machine you a pan spacer and get another quart in the pan (with a longer pump pickup too of course) and that should help out.

Definitely check the timing and fuel mixture.  Lean mixtures make bikes run hot, and forced-induction aggravates it.  Also, the timing is going to be retarded somewhat because of the turbo.  It might be that someone has retarded it too far to make up for running crappy fuel.  That bike's gonna expect (and need) premium to keep the knocking down under boost.

NitroHunter is definitely more the expert on turbo SOHC's here, though.

Offline myhondas

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Re: turbo charged 71 Honda 750
« Reply #8 on: August 11, 2009, 02:23:13 pm »
and a oil cooler will help.... I had one on my original 750 and never saw the bike overheat. depends on the size of the cooler coil whether or not it is effective.
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Offline PxTx

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Re: turbo charged 71 Honda 750
« Reply #9 on: August 11, 2009, 04:57:40 pm »
Would you mind posting a pic?  I think it would help with answering your question.  Really sounds like a cool bike!

the glass man

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Re: turbo charged 71 Honda 750
« Reply #10 on: August 12, 2009, 07:03:03 pm »
Thanks alot for your ideas,
      I changed my oil, and used 40 wt. It gets really hot 90 when I rode in town. Also when not in 90 degrees and the engine is cold, it a good 5 min. to warm up get out on the rode, low end it seems that the plugs are fouling. Get down the rode one mile and it clears away.I think I will change the plugs.
      I had electronic ignition a log time and lots of trouble with it. If I rode inthe rain it would quit running. when it would dry up it would run again. So I had it removed, the company would not make good for it.
      I would like to add photos But I have not been successful I'l try again--Tony
I tried to post photo of bike 413 it's to large

Offline NitroHunter

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Re: turbo charged 71 Honda 750
« Reply #11 on: August 13, 2009, 09:46:12 am »
I have taken the liberty of posting some of Tony's pics & info from an e-mail he sent to me:
 
"I bought my bike in '71, brand new, and had a great time with it.
About two years later I decided to go turbo, American Turbo Pac. In addition
to turbo, the engine was done up with yoshimura parts; pistons, valves, valve
springs, cam. I believe complete.
I have a boost gauge and it's set at 10lbs. Years ago I was able to pick
up a 75 Super Sport gauge assembly consol.
I drove it from N.Y. to Florida to Daytona races. I have lots of biking stories logged.
I live in the Florida Keys not far from Key West."
« Last Edit: August 13, 2009, 10:15:35 am by NitroHunter »
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Offline JLeather

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Re: turbo charged 71 Honda 750
« Reply #12 on: August 13, 2009, 11:05:03 am »
That's awesome that he's put that many street miles on it.  Makes me feel better about how much life I can expect out of the one I'm building.  I think I can see what might be part of the problem.  Yosh didn't make any turbo pistons that I'm aware of.  They're pistons were pretty high compression.  10 pounds of boost on top of a Yosh 823 kit would make for a really high compression motor.  probably has the timing set pretty far back to compensate, and retarding your timing too far will definitely make the motor try to run hot.

Glass Man, do you remember the pistons that went into the bike?  What's the timing set at as far as max advance?

Offline andy750

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Re: turbo charged 71 Honda 750
« Reply #13 on: August 13, 2009, 05:55:39 pm »
Very cool! Love the photos, thanks!

Cheers
Andy
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Offline scartail

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Re: turbo charged 71 Honda 750
« Reply #14 on: August 18, 2009, 05:52:27 am »
What about numbers? Got any performance specs? Has it been on the dyno/strip?
'89 Hawk GT, newly acquired, daily beater...
'76 CB550, was my daily beater... my cafe project...
'72 Yamaha R5, newly acquired project... donated to my buddy...
'67 Suzuki T20, still working on her too... Currently in pieces...

 

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