GS1150E big bore kit

[Gregg]

Hello all, I'm new to the board. I'm also a big fan of the GS1150. I had two brand new ones , one ES faired model in 1984 and one E unfaired model in 1985.

Curently I have an 85 GS1150 with just on 12K on the clock. It is stock except for 4 into 1 pipe and 36mm RS Flatslides. I am considering running a big bore kit. I don't drag race but am looking for a reliable hot rod for the street.

I'm considering the following options:
1230cc kit w/10.25:1 compression
1327cc kit w/ big block and 7.8:1 compression
1327cc kit w/ big block and 11:1 compression

Which do you think would be the most reliable for the street? Living close to Chicago I occasionally may get stuck in rush hour traffic. Would the 1327 with lower compression yield more power than the 1230cc kit with higher compression? If I went to a 1327 size would I have to swap out my 36mm flatslides for 38mm?

One other option may be to go turbo but I doubt that my $$ will be that long. Thanks in advance for your help!

 

[Nessism]

Those 7.8 pistons are for a turbo right?

 

[Gregg]

7.8 pistons

7.8 pistons

Actually I originally thought they were turbo pistons to by APE told me they were not due to the location of the rings on the pistons.

 

[Guest]

They are turbo.

How much head work do you intend to do? If not much, go with the 1229.

Jay

 

[rapidray]

I build 1229s all the time & they are great "bang for the buck"! I build BIG motors also but a 1229 is the least expensive of your choices. It's not difficult to get 150 at the back wheel with a 1229 but it DOES require headwork to do it. You already have carbs so pistons, cams, springs, porting, & a GOOD valve job will get you there. There are other things you will need though. A modified clutch hub, oil pump gears, cam sprockets, cam chain tensioner, valve seals, cam chain, etc... It all ads up but can be a VERY fun package & very durable & user friendly when done correctly. Let me know if I can help you. Ray.

 

[Gregg]

Thanks Ray for the great feedback! My intuition was telling me that but my addictive mind (5 yrs sober) was telling to go to the extreme. Also thanks for the "beef up" advice. I plan to do some headwork and clutch work but did not think about the cam chain and oil gears. Thanks again.

 

[Gregg]

Jay are you from APE? I thought the 1327 7.8:1 pistons would be turbo. I thought about going that route in case I wanted to add a turbo later. When I called an APE tech he told me that they were not turbo pistons due to the location of the rings on the pistons. I never heard that before put assumed he knew what he was talking about. What are your thoughts? Thanks.

Someone, I forgot who, told me that a 1327 big block would run cooler than a 1229 because there is more meat around the cylinders. I probably will go with the 1229's , like Ray says just because of the cost.

 

[rosco15]

Jay,
Doesn't the big block run hotter due to no air flow thru the block?

 

[rapidray]

The big blocks run HOTTER because there are no air passages BETWEEN the cylinders. I still run them on the street but there ARE things you have to do for additional cooling to make them work WELL in traffic. Ray.

 

[gs1197]

Would anyone happen to know if there are any other (1150) 1230 12.5-1 piston kits beside MTC?
So far haven't been able to find any other off-the-shelf sets available. Don't need or want any custom made.
And for the record, don't have anything against MTC...have always treated me right....just thought it strange haven't been able to find anything else.
Thanks,
Mike

 

[rosco15]

Wiseco does the 1229, but 10.5-1 compression.

 

[RacingJake]

Now this is just me but MTC pistons and me don't get along. I do just fine with Wiseco's but would like to try some JE's next if my Wiseco's ever go south one of these decades.

 

[rapidray]

I can get you CUSTOM made CPs for $650.00 a set. How much will the MTCs cost you? Ray.

 

[gs1197]

I can get you CUSTOM made CPs for $650.00 a set. How much will the MTCs cost you? Ray.

$517 according to their website.

 

[rapidray]

I GUARANTEE the CPs will be lighter, stronger, & make more power! Also, for the price I quoted you, that includes lateral gas porting, anti-detonation grooves, pin oiling, GOOD pins, locks, & gas nitrided rings. MTC doesn't even have top of the line rings. The best you can get from them is a moly top ring. Less expensive is ok for some people but when I build a race motor for a customer I only use 1 brand of piston. Ray.

 

[4cyl h2]

I GUARANTEE the CPs will be lighter, stronger, & make more power! Also, for the price I quoted you, that includes lateral gas porting, anti-detonation grooves, pin oiling, GOOD pins, locks, & gas nitrided rings. MTC doesn't even have top of the line rings. The best you can get from them is a moly top ring. Less expensive is ok for some people but when I build a race motor for a customer I only use 1 brand of piston. Ray.

Ray what are anti detonation grooves and what do they look like even more inportant how do they work? also what is lateral gas porting?

 

[jstewart]

I build 1229s all the time & they are great "bang for the buck"! I build BIG motors also but a 1229 is the least expensive of your choices. It's not difficult to get 150 at the back wheel with a 1229 but it DOES require headwork to do it. You already have carbs so pistons, cams, springs, porting, & a GOOD valve job will get you there. There are other things you will need though. A modified clutch hub, oil pump gears, cam sprockets, cam chain tensioner, valve seals, cam chain, etc... It all ads up but can be a VERY fun package & very durable & user friendly when done correctly. Let me know if I can help you. Ray.

Ray I had two GS 1150E's in the 1980's both of them 1198's, ported and set at 11/1 comp., web drop in cams, 36 mm flat slides, welded cranks, APE cam chain tensioners, Falicon clutch baskets. They were both dead reliable. I don't know what the HP was but they both ran consistent mid 6.70's at 106 to 107 MPH in the I/8 with stock wheelbase and ride height. Will this 1229 150HP engine package survive on the street at this HP level without welding the crank and using straight cut gears on the crank and clutch basket?? I didn't have the straight cut gears but I never ran a slick and bars. At a minimum I would weld and check the crank indexing for a motor this strong. I assume crank welding was included in the etc. you referred to.

 

[rapidray]

1150 cranks are already welded & reliability is no issue at this power level. The straight cut gears aren't really an issue until 170-180 or so hp, or till you run a slick. Call me at 714--356-784five if you ever have questions.
Ray.

 

[jstewart]

1150 cranks are already welded & reliability is no issue at this power level. The straight cut gears aren't really an issue until 170-180 or so hp, or till you run a slick. Call me at 714--356-784five if you ever have questions.
Ray.

Thanks Ray, my 28 year old memory about the crank welding is obviously fuzzy. Thanks for the phone number, I will call when I reach a stage in the restoration of the 85 GS 1150E I recently bought where I need help. I agree about the quality of CP pistons, I have used them exclusively the last 10 years.

John

 

[trippivot]

CP pistons are in my big engine race bike. love 'em. after a whole season I tore down the top end and could not believe how light the wear marks were. ball hone, reinstall, keep on racing. third year and I'll skip the off season teardown.

just to add -I have put together an engine using a welded heli gear small end crank - I am going to run nitrous on a pro street chassis and see if it will last a season. thinking about spraying enough to run 9:50 street fighter index.