Did Yoshimura make engine heads?

[Anonymous]

I have my 1978 GS 1000 in to my mechanic who is doing a complete re-build. Aparently my bike was used in superbike races in Cali by some dutch guy before I acquired it. It's overbored, has racing suspension and shocks, a Yoshimura tank, blah blah blah. Basically it's too racy a bike for some one with such little experience.

I just got an e-mail from him saying that the valve and valve guides need to be replaced, and that it's a Yoshimura head. Did Yoshimura even make such a thing? If so, is it worth preserving, or should I just find the cheapest option to make this bike run?

Thanks!

[humhead]

I'm pretty sure Yoshimura didn't pour the casting, but they modified the Suzuki part. If is is a genuine yoshimura modified head, it's definitely worth preserving. So is the rest of the bike. What are your plans for your vintage racer?

Terry

[Anonymous]

Plans??

I'm trying to have it restored to a state where it's legal and reasonably easy to ride in normal traffic.

Previous owners had:

* Cut part of the rear frame off
* Removed all safety equipment except for front and rear light
* Put in racing clutch springs, brakes and suspension
* Re-jetted the carbs
* Increased the cylinder bore from 70 to 73 mm
* Put on a Yoshimura tank
* Kerker 4:1 exhaust (at least that's the muffler, not sure about the pipes themselves)
* Aparently had Yoshimura modify the head.

Frankly, I don't know what else was done to this bike. This is just the stuff I know.

So, for me, the following are priorities:

* Get the engine running smoothly and comfortably idling when not racing. (it idled very badly before)
* Reduce clutch tension so I can sit in traffic without cramping.
* Add necessary safety gear: Turn signals, and horn
* Re-paint or sand blast where needed.

My mechanic is pretty much rebuilding the engine. He's sandblasted and painted where needed, he's replaced the cilinder rings. Now he's asking if I'm ok with the additional $500 on top of the $3,600 estimate for the rest of the work.

I would hate to not take advantage of some vintage Yoshimura work, but $500 is a major part of my school budget this semester.

Thanks for any advice!

Erik

[Mysuzyq]

Just curious...why spend all that $$$ restoring a performance bike to stock? $4,100 + the cost of the bike.....for that much $$ or even less you could find yourself a pretty mint stockGS more suited to your riding style & easier to manage in traffic.

Check this for an idea of what prices are....

http://cgi.ebay.com/ebaymotors/Suzuki-GS-1100ES-1983-Suzuki-GS-1100ES-Motorcycle_W0QQcmdZViewItemQQcategoryZ6027QQitemZ4567482205QQrdZ1QQsspagenameZWDVW

http://cgi.ebay.com/ebaymotors/Suzuki-GSX-Katana-GS-1150EF-1985-GS-1150-EF-LQQK-Like-New-Lo-Miles_W0QQcmdZViewItemQQcategoryZ50028QQitemZ4567941969QQrdZ1QQsspagenameZWDVW

The bike you have is set up to run best at high rpm, but they are no fun at all in slow moving traffic situations.

A lot of the performance bits on this bike will fetch decent money on ebay....I am guessing it has Yosh racing cams in the ported/flowed head, which could account for the poor idle/low rpm performance.... I imagine you would find a few takers here on the GSR if you choose to sell this bike in whole or parts...and more than a few will happily swap you stock parts for the yosh stuff you take out


Tony.

[KGB]

whoa whoa....


Before you start cutting this bike and sell it on ebay......

Got a picture of the bike? In one piece or some close up shots?


You may or may not have vintage machine there.

I'd be willing to part with a well running 1982 GS1100E, with about 12K miles on it for your 1978 GS1000

[Anonymous]

No no not parting it out....

I'm not parting out this bike.

The only small performance mods are to the clutch springs, and carburator jetting.

If I can't get the bike to run smoothly with that, then I'm going to sell the thing as a whole, becuase it would be a shame to take it apart for parts.

IN addition, I'm having safety equipment replaced. Unless some one here wants to pay me extra to leave the safety equipment off (turn signals, lights) that's pretty much it.

I'm not trying to restore the bike to 100% stock. I'm just trying to get it to be a little more refined on the street is all.

[robinjo]

Do you have any pictures of the head? I would find it interesting to see the in and outlet tracts. I have a good head of a '78 GS1000 in my workshop sans valves, only problem is a broken off hard thing where a exhaust bolt should be and the shipping costs...

[Anonymous]

Pics

I'm having the bike restored at Bikeworx in Maynard, I'll see if Galen will let me take some pics before he bolts the head on.

What exactly do you want to see?

Erik

[Einar J Skog]

HI

* Aparently had Yoshimura modify the head.

Belive Yoshimura made a shims below bucket version for their racing bike.
(GS1000 8valve with 130HP) In 1978 I think.

GS1000GLx +++++

[humhead]

I found this excerpt from an article in Cycle World describing the Yosh AMA superbike.

Pops Yoshimura believes in extensive cylinder head porting and polishing. In finished form, his ports look more like modern art than a hunk of machinery. A view into a port reveals flowing lines and delicate shading patterns as light swirls onto the shimmering metal. The object is to remove flow reducing, rough cast surfaces and edges and straighten out curved sections. Yoshimura points out that at 10,000 rpm, the cylinder must be filled with a gas/air mixture in just 0.012 seconds, or 83.3 times per second. Intake port mixture velocity reaches more than 280 mph. Every turbulence producing port defect effectively reduces the port area and decreases flow, and at high rpm/high port velocity, small defects are significant.
In his quest for maximum flow (and power), Pops increased the size of the valves. A stock GS1000 has 38mm intake valves and 32mm exhaust valves; the Yoshimura GS1000, 39mm intake and 34mm exhaust. Total valve area is thus increased 8.5 percent. Each valve is shaped for better flow at the tulip area. Valve face angle is a conventional 45'. Stellite is welded onto the valve face and stem tip for hardness, while an overall nitride treatment reduces stem friction within the Yoshimura nickel bronze valve guides. Again in the interests of maximum flow, valve stem diameter is reduced 0.4mm, from 7mm to 6.6mm the narrower stem takes up less room in the port and allows better flow.
Heavy duty valve springs, anodized aluminum retainers and special titanium keepers dimensionally identical to Honda keepers from the original CB750 (which are larger and shaped differently than the stock Suzuki keepers) replace the standard parts. Instead of the stock valve buckets with large, adjustment shims riding between bucket and cam lobe, the Suzuki Superbike uses lightweight Yoshimura racing buckets with small adjustment shims located underneath. Radical camshafts tend to kick out stock shims at very high rpm, usually destroying the cylinder head in the process. That isn't a problem with the shim moved underneath the bucket. What's more, in combination with the other racing parts, the lighter buckets help reduce valve train weight by 40 percent.

If you have anything like what's described above, it's VERY valuable. I don't think it's a good idea to run this head on a street bike. You might consider restoring it to it's original race configuration. If you do decide to make it street legal, try to do things that are easy to undo.

Terry

[Anonymous]

Hmmm, still have the normal shims over bucket...

But I'm assured that it's a Yoshi head.

The head is at the machinist getting new guides. As soon as it's back I'll take some pics for the group.

The tank is silver and says Yoshimura under the Suzuki label. Rest of it is black. Original rear foot rests were removed when the frame was cut down.

Can't wait to load it up with saddle bags and rhinestones....... :twisted:

[humhead]

Can't wait to load it up with saddle bags and rhinestones.......

What, No FRINGE

[Big Jay]

I found this excerpt from an article in Cycle World describing the Yosh AMA superbike.

Pops Yoshimura believes in extensive cylinder head porting and polishing. In finished form, his ports look more like modern art than a hunk of machinery. A view into a port reveals flowing lines and delicate shading patterns as light swirls onto the shimmering metal. The object is to remove flow reducing, rough cast surfaces and edges and straighten out curved sections. Yoshimura points out that at 10,000 rpm, the cylinder must be filled with a gas/air mixture in just 0.012 seconds, or 83.3 times per second. Intake port mixture velocity reaches more than 280 mph. Every turbulence producing port defect effectively reduces the port area and decreases flow, and at high rpm/high port velocity, small defects are significant.
In his quest for maximum flow (and power), Pops increased the size of the valves. A stock GS1000 has 38mm intake valves and 32mm exhaust valves; the Yoshimura GS1000, 39mm intake and 34mm exhaust. Total valve area is thus increased 8.5 percent. Each valve is shaped for better flow at the tulip area. Valve face angle is a conventional 45'. Stellite is welded onto the valve face and stem tip for hardness, while an overall nitride treatment reduces stem friction within the Yoshimura nickel bronze valve guides. Again in the interests of maximum flow, valve stem diameter is reduced 0.4mm, from 7mm to 6.6mm the narrower stem takes up less room in the port and allows better flow.
Heavy duty valve springs, anodized aluminum retainers and special titanium keepers dimensionally identical to Honda keepers from the original CB750 (which are larger and shaped differently than the stock Suzuki keepers) replace the standard parts. Instead of the stock valve buckets with large, adjustment shims riding between bucket and cam lobe, the Suzuki Superbike uses lightweight Yoshimura racing buckets with small adjustment shims located underneath. Radical camshafts tend to kick out stock shims at very high rpm, usually destroying the cylinder head in the process. That isn't a problem with the shim moved underneath the bucket. What's more, in combination with the other racing parts, the lighter buckets help reduce valve train weight by 40 percent.

If you have anything like what's described above, it's VERY valuable. I don't think it's a good idea to run this head on a street bike. You might consider restoring it to it's original race configuration. If you do decide to make it street legal, try to do things that are easy to undo.

Terry

It could be duplicated only better for about $2000.

Jay

[johnrregan]

yoshimura engines for sale

at the stafford bike show in the uk later this month, there is an auction of bikes and bits, amongst the stuff selling is a one off bike built by uk bike race tuner pip higham, a gsx11 thats been modified to make it a 1600cc SIX CYLINDER bike!!! and stunning it looks too, totally unique. anyhow, amongst his other items for sale are two complete and unused 16 valve 1000cc gsx derived yoshimura works race engines!! be interesting to see what thy will go for.

[ToddB3]

I've seen a Wes Cooley vintage racebike at the Barbers Motorsports Museum in Birmingham that had Yoshimura stamped on the side of the head.

Todd