Engine Build Advice for 78 GS1000 Roadracer

[rcp]

Hi,

I'm rebuilding the engine for "HMCS Dreadnaught", my '78 GS1000 roadracer. I campaigned it last year in the VRRA's Period 3 Heavyweight. This year I'm aiming to capture the P3Heavy points title, and would prefer not to have to do it on skill alone. Of the four tracks we visit, only Mosport's a real horsepower circuit - it's got a long uphill straight that had a couple of bikes check out on me last year. The other three are short and tight. So I'd like to keep the great low-end grunt, while adding top-end.

I haven't been deep into an engine before, so am looking to learn as much as I can, but avoid leaning from personal experience. I've bought an 1100 Wiseco big bore kit and a set of well-rebuilt 33mm Mikuni Smoothbores. I've gathered some tools to do a DIY port job. I've got the factory and Chilton shop manuals, the Honda Common Service Manual, and Kevin Cameron's and Jewel Hendricks' books as guides.

What I don't have any of is experience. Which leads me to two questions:
1) What advice would you give someone embarking on their first engine rebuild?
2) What makes GS engines run well? (What make more power, and what keeps them together?)

I've got some basic ideas for more power - more displacement, more compression, more airflow probably lead to more power, but I'm not sure what to prioritize. As for keeping it together - a manual cam chain adjuster and an oil cooler are probably the basics. But what about welding the crank? Is that only needed for drag bike power levels?

Your experience and advice will be much appreciated.

Thanks!
- Richard

PS. I should mention that the previous owners have done a very good job of sorting the handling - reworked GPZ front end, reworked marzocchi shocks, GS1100 aluminum swingarm, 18" GSXR-rear GPZ-front wheels, a bunch of weight removed - including charging system and starter. It's a bit long of wheelbase in the hairpins, but handles like a dream everywhere else.

 

[rcp]

Rob Muzzy's Ten Commandments of Racebike Building

Rob Muzzy's Ten Commandments of Racebike Building

As a reminder to myself, here's the Ten Commandments, as brought down from the mountain by Kevin Cameron:

Rob Muzzy's Ten Commandments of Racebike Building

1. Analyze the work to be done -- reliability first, performance second.
2. Work on jobs that pay off quickly. Don't pin down talented people on low-yield projects.
3. Keep away from the dyno and the flowbench unless you know what you want and why you need it.
4. Run combinations that work together. An engine is a system, not a parts list.
5. In a system of parts that must work together, choose the cheap parts to complement the expensive ones.
6. If there are two good ways to do a job, one simple, the other complicated, use the simple way.
7. Use everything you know in your work, even if it seems irrelevant.
8. Do everything you can in your own shop.
9. Have enough of the things you know you'll need.
10. Big numbers on the dyno are no substitute for races won.

 

[duaneage]

If money is no object you can buy a lot of performance already packaged and not risk making a mistake on a big project. I've done a few engines and I measure and clean everything carefully while taking my time to do it. I've stil made mistakes but learned from them.

The 1000 is a good platform to begin with, the engine is solidly designed. The head from an 1100 should fit, not sure what the valves and combustion chambers are like between them but ask what the differences are. Bigger cams need more compression with in turn needs better gasoline. If you make the leap to bigger bump sticks you're in high compression land and avgas may be required.

Since you are planning a race bike streetability is not the first concern but no one likes a bike that idles bad or is hard to start. There are bound to be tuning requirements outside the ordinary. Keith KRause knows these engines and is a member here, contact him.

I always look at the cost of a part and what it delivers when deciding if it is worth it. I like parts that improve efficiency since that is free horsepower. Light weight parts are a key component, shaving even more weight off the bike is better than trying to wring more power from 1000 cc.

If you have never rebuilt an engine before (and this sounds crazy) rebuild something simple and cheap for the experience. Learn to do things like mic bores, ring pistons, hone cylinders, measure journals, clean parts, apply gaskets, and inspect and measure everything. Then go on to the multi million dollar engine.

 

[Nessism]

There is lots of good info in the archives here. Learn to use the Advanced Search function to dig it out.

I'm not an expert on this but I've learned enough to know that porting is best left up to the experts. Smoothing out the casting flaws is fair game I suppose, and maybe a little smoothing the transission between the as-cast portion of the port and the machined sections, but that's about all you should do. Back cutting the valves has received favorable mention here so again, use the archives for more information.

Good luck with your project and don't forget to post some photos for us as you go.

 

[bwringer]

first_timer has done a lot of research along these lines (building a reliable GS1000 monster motor) as well. You might try to PM him or search for some of his old threads on the topic.

 

[sharpy]

Pop on over to http://oldskoolsuzuki.info/ Craig Smith has a 150hp 1000 that he has just finished his race carrier on.

 

[rcp]

Thanks for the advice guys. Progress so far is some disassembly - removed cylinder head and cylinders. I found a serviceable valve spring compressor at Princess Auto for the princely sum of $50. From a quick eyeballing things look good so far - time to clean things up and

Photos:
http://www.sentientmeat.ca/~rcp/photos/2009-GS1000-engine/

Good luck with your project and don't forget to post some photos for us as you go.

I going to attempt to keep up with photos - usually I'm too busy doing stuff to take the time to photograph it. There's photos here of the seat I'm working on as well.

first_timer has done a lot of research along these lines (building a reliable GS1000 monster motor) as well. You might try to PM him or search for some of his old threads on the topic.

first timers's "Yosh build part deux"
http://www.thegsresources.com/_forum/showthread.php?t=132169
I've been following that one.

Pop on over to http://oldskoolsuzuki.info/ Craig Smith has a 150hp 1000 that he has just finished his race carrier on.

He has some great photos. His username there is "Craig Smith Smithy" is anyone else is looking.

I think this highlights what I'm really looking for. I can come with a list of things to do to a GS1000 to make lots of power and keep it together, but I don't know what are the priority items (the "big rocks first" in that metaphor). I should have this bike for years, so I don't have to do everything right away (nor can I afford to), and incremental improvement is a nice way to work. If it were your limited time and limited money, what would you tackle first?

- Richard

 

[first timer]

Let me ask this how much do you have to spend? (this is the most imporant question)

things to think about are doing things once that you don't have to do later. I would pull your crank, get it rebuilt by GRC add a straight cut gear and have stan rebuild the clutch. The stock helical gear will cause the basket to shatter under race condtions plus stan tells me the straight gear free up HP too. If you have enough money i would also under cut your gears too since the cases are split. You may also want to media blast (aluminum oxide @ 40psi) your cases and then paint them with gun kote 2400 this will give you 15% increase in cooling.

Once you do that now you have a solid motor and will not need to split it again. You can now spend more money or ride it the way it is until you get more, all the work about will set you back around 2K.

If you have more money go with the 1100 kit.

if you have even more money get your head ported, ($1500) I could give you some pics but it won't do you any good, porting is a black magic/art and takes years of trial and error to get it right. It's not about how much you can flow but how fast and how it goes in. My porter did my head so that in the future i can upgrade to bigger valves and cams when the money tree regrows. But the head will do very good using stock valves and a bigger cam.

if you have even more money get some under shim buckets and TI retainers for the bigger cams and higher rpms

and last but not least look into a after market ignition, my tuner is a big fan of msd but lots of folks like the dyna 2000.

Also don't forget the carbs this assumes you already have a set, but if you don't, consult with you porter with what would be best.

Speedysteve over at oldskool is my porter and knows a ton and has good race resume.

Like said above you could save a few bucks and hold off on the port and run a 1100G 8v head they will flow better then the small port stuff and they have the D exhaust port too to help too, just check to make sure race rules let you.

Basically you need to have a war chest of about $5K to $7K depending on how hard core you want to get on this motor.

-Ryan

 

[rapidray]

I do a lot of engine builds each year & for a lot of different scenarios. I will tell you in all SERIOUSNESS that if you don't have head porting experience, you should find someone that does because you can wreck the head VERY quickly by doing the wrong stuff. I do probably between 25 & 35 heads a year of all types of 4 stroke engines & have seen guys make good heads into junk inside of 10 minutes. Let me know if I can help, Ray.

 

[SqDancerLynn1]

I saw a welded GS1000 crank on Ebay !!! As Ray said Don't do any porting if you don't know how, consult an expert

 

[rcp]

Talked with rapidray on the phone, and he's now the man for the cylinder head.

I'm trying buy a local set of carb boots to fit the VM33 smoothbores, but he's unsure about selling them, so I may have to order new.

I've got a phone message in to Gardner to find out about welding the crank, replacing the helical cut gear with straight cut, and reinforcing the clutch.

Thank for the pointers all, on the ebay welded crank, but I decided to pass on that, as I'd prefer to build the existing one up better. The engine I'm after is a bulletproof version of the existing one, with the freight-train (or battleship in this case) broad and flat torque curve bumped up a big chunk.

- Richard

 

[not a biker]

raising compression 1/2 to 1 ratio over stock is free horse power over the entire RPM range. but heat in a air cooled engine is death. also octain ratio will come into play. it is hard to get a racing cam that makes more horse power all over the RPM range. pic a cam that will help the mid range and the top end RPM range. peak horsepower numbers are not the answer.

 

[first timer]

Another thing to think about is when doing your motor, you need to decide if you want to run racing gas like VP racing fuel only (which is fine if you are only racing) or street gas. With the VP stuff you can go bigger CR without knock plus the VP delivers more energy then regular gas. I wouldn't worry much about heat especially if you do the gun kote and then go to a bigger oil cooler like a earls 14 row or something. You are in good hands with Ray I am sure he can help you figure out what is best for you.

 

[rcp]

Talked to Stan Gardiner today, and after finding out just how much it costs to go with the full rebuilt crank and clutch with straight-cut gears replacing the helical, I'm starting to wish I had pounced on that welded ebay crank. I have not yet decided how far to go with the bottom end. (APE's up-down undercut on the gear dogs would also be nice).

I'm definitely going to 1100cc, and VM33 smoothbores as I've already got those. The head is going to rapidray, as soon as I locate carb boots for the VM33s. I've talked with Ray regarding milling for more compression, and will very likely be doing so. Running race gas is fine, as this is a track-only bike. I've got an oil cooler coming my way from Nessism.

I'm talking to a local kawi guy about shim-under retainers and buckets from KZ/GPz 550, 650 that may fit. He's got a GS1000G head so is going to double check.

I'm as yet uncertain how much I'm willing to spend. I had started off wanting to spend the minimum to prevent my main competition from just out-pulling me a little up Mosport's long uphill back straight. Then I thought about the two guys who checked out entirely on that straight in the first lap. Now I'm starting to suffer from "while I'm in there" project creep. It would be a shame not to go whole-hog on the crank if it's going to be done at all.

- Richard

 

[first timer]

it's only money .... here's your glass the koolaid tastes great.....

The Kz stuff won't work, i explored that route, Jay at APE sez the KZ under buckets are .5mm smaller then GS buckets. Ape has GS under buckets. The KZ stuff might work but it will be a little loose and might wear faster, but i really don't know how bad .5mm is.

You should be able to use your stock boots just ground out to fit the 33's. Your tuner should be porting and grinding the boots to match the head when doing his work.

If money is tight try running your bottom end as is, just make sure it is straight. It might twist it might not. Just don't hammer it from a dead stop or drop it down a few gears and drop the clutch. But the very least keep your stock clutch but get it rebuilt HD stlye. That should keep it together.

 

[trippivot]

the helical gear is A-OK up to 150 horsepower. and 11,500 rpm .MAXIMUM.

you are not going to need the full blown crank job. just a welded low mileage unit is fine.

back cut 2 and 3 gear is well worth the time.

shim under is good for hi cam lift and hi rpm. suzuki BUCKETS NEEDED
kawasaki retainers and springs do interchange. KEEPERS are suzuki too.
not necessary until .425 lift . other work is also needed to do this.

get a 73.5mm piston kit

mill your head .090 or so. run 110 fuel. re work the piston valve pockets due to the milling changes exact location of valve at full lift.

get a manual camchain adjuster- (learn to set it right)

get the suspension set up right. proper race sag/ ride height ( 3% better suspension effy. is the same as 10% more engine power.)

Gear ratio is very important!! Red line maximum at the end of the longest straight or the finish line in a specific gear.

lighten the hell out of the bike. remove any non essential anything.

 

[rcp]

it's only money .... here's your glass the koolaid tastes great.....
[...]
You should be able to use your stock boots just ground out to fit the 33's. Your tuner should be porting and grinding the boots to match the head when doing his work.

I'm not sipping the koolaid - no,no,nope.

The stock boots don't look to me like they'd work - they're only ~45mm O.D. and the carb spigot diameter is 40mm (42mm at leading lip). I think I've found the right ones (part # 002-053 at Sudco). I've got PM off to Renobruce to confirm, as he's got the same carbs and head for his Beat project. I'm going to call Sudco & APE to ask as well.

the helical gear is A-OK up to 150 horsepower. and 11,500 rpm .MAXIMUM.

you are not going to need the full blown crank job. just a welded low mileage unit is fine.

Which is why you're going to sell me yours, right? Right?

- Richard

 

[rcp]

back cut 2 and 3 gear is well worth the time.

shim under is good for hi cam lift and hi rpm. suzuki BUCKETS NEEDED
kawasaki retainers and springs do interchange. KEEPERS are suzuki too.
not necessary until .425 lift . other work is also needed to do this.

get a 73.5mm piston kit

mill your head .090 or so. run 110 fuel. re work the piston valve pockets due to the milling changes exact location of valve at full lift.

get a manual camchain adjuster- (learn to set it right)

get the suspension set up right. proper race sag/ ride height ( 3% better suspension effy. is the same as 10% more engine power.)

Gear ratio is very important!! Red line maximum at the end of the longest straight or the finish line in a specific gear.

lighten the hell out of the bike. remove any non essential anything.

I hear you both on the Kawi retainers. No luck there.

It's certainly light now!:

The previous owner removed a lot of weight, including all the charging system and starter. He's cut out most of the sprocket cover, and he got a low-clearance, lighter left-side engine cover welded up out of the original:


I've got a local vintage roadracer (builder of this bike, and previous owner two owners ago) asking his drag racing buddy if he's got any used H.D. valve springs. The roadracer has successfully used four of those paired with a stock (big HD, small stock on intake/big stock, small HD on exhaust) in the past with stock and mild cams.

- Richard

 

[first timer]

post up what you find out about the boots, I may end up going 33's if my 29's are to small.

 

[Guest]

post up what you find out about the boots, I may end up going 33's if my 29's are to small.

Here's what looks to be a nice set on ebay right now. With pods!

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=170302220574&sspagename=STRK%3AMEWAX%3AIT&viewitem=