Maximum bore/stroke for a 1200?

[jeffro]

Hi everyone, I introduced myself in the welcome section.I just picked up a 88 Vmax through craigslist with only 16K mi, and although I'm trying to clean it up and get running at this time,debugging dead battery ,fresh fuel and oil etc. The previous owner kept mentioning this particular bike as being 1800cc .I told him at purchase time that's impossible as factory their only 1200cc.He went on to say that this bike ,the previous owner (i'm the 4th owner) had bored out to 1800cc is that possible? Personally the guy I bought the bike from I think is full of sH%*T,but the thought still remains at the back of my mind.Is this possible?:confused2: There are visible mods to the bike like a vboost toggle switch that is supposed to change the power output .Oh I also got goodies with the bike like a set of progressive rear shocks, progressive springs for up front. it's the first Vmax I've ever bought I know nothing about this bike other than what I've been reading on this forum. "weak second gear horror stories come to mind" Yikes!!!any suggestions?

thanks Jeff

 

[ninjaneer]

1800? that'd be a first. the biggest i've heard is 1500.

Regards from my Taptalking Hercules Android

 

[Redbone]

Sean or others may know definitivly, but I've heard of a 1700+ cc motor. It won't be long until you get your answer.
Oh and welcome to Vmax Forum. It sounds like you have a lot of work to do, just know you are in the right place to get all the help you need.

 

[ninjaneer]

wow! 1700 bored? dayum! how cool

Regards from my Taptalking Hercules Android

 

[twistedmax]

Ive only heard of as big as 1570,I belive that Paul(madmax) may have expairmented with bigger bores but nothing that was reliable. what kind of HP did the previous owner claim your bike to have?

 

[Rusty McNeil]

I think the guy is full of dog poopie....

I don't know the exact dimensions but a sleeve to handle a huge bore is eventually going to start using up room in the water jacket around the sleeve....

Stock bore is 77mm, I believe 87 is about as big as they go without getting all weird with the cases if you have the money....I think I saw a pic floating around on the internet years ago of one that had external piping to supply the water jacket....I would for sure consider that one wierd....

Without resleeving I believe 80mm is max over bore...

PCW's 1500 is 85mm over bore using stock stroke.

Mines a 1539cc's using 83mm bore and 5mm stoker crank...

I have no idea how much they can be stroked, although I think it can go more than the 5mm we went with on mine, I think the stroke can go as high as 75mm...Sean was the brains behind mine.....I just assembled it.......(and am very happy with the resultsunk

Just for grins I ran PCW's max bore of 87mm (advertised for their 1570 long rod motor) and the 5mm stroker crank I have thru a calculator and it yields 1690cc's.......

So I'd say 1690 is possible without getting really wierd with it.....:ummm: Reliability issues tho???

If you run PCW's max long rod engine bore of 87mm and Seans 75mm stroker crank thru the calculator you get 1780cc's

Of course the engine is going to cost 4 times what you paid for the bike...:rofl_200:

 

[srk468]

Like Rusty said I do believe you could get close probably but with that much stroke it probably wouldn't rev real high.... I think the more likely case is the guy was full of shit LOL

Sent from my HTC Rezound using Tapatalk 2

 

[ninjaneer]

I think the guy is full of dog poopie....

I don't know the exact dimensions but a sleeve to handle a huge bore is eventually going to start using up room in the water jacket around the sleeve....

Stock bore is 77mm, I believe 87 is about as big as they go without getting all weird with the cases if you have the money....I think I saw a pic floating around on the internet years ago of one that had external piping to supply the water jacket....I would for sure consider that one wierd....

Without resleeving I believe 80mm is max over bore...

PCW's 1500 is 85mm over bore using stock stroke.

Mines a 1539cc's using 83mm bore and 5mm stoker crank...

I have no idea how much they can be stroked, although I think it can go more than the 5mm we went with on mine, I think the stroke can go as high as 75mm...Sean was the brains behind mine.....I just assembled it.......(and am very happy with the resultsunk

Just for grins I ran PCW's max bore of 87mm (advertised for their 1570 long rod motor) and the 5mm stroker crank I have and it yields 1690cc's.......

So I'd say 1670 is possible without getting really wierd with it.....:ummm:

If you run PCW's max long rod engine bore of 87mm and Seans 75mm stroker crank thru the calculator you get 1780cc's

Of course the engine is going to cost 4 times what you paid for the bike...:rofl_200:

learned something new--how you stroke it matters as much as how you bore it. lol. let the jokes begin. hahaha. but seriously i'm learning so much motor theory from you folks. thanks a bunch.

Regards from my Taptalking Hercules Android

 

[wildweasel_pt]

Some time back i saw something about an engine that was bored to those specs but ditching the waterjacket. That engine was to be used for drag racing and special fuel had to be used due to heating and lack of refrigeration. I don't remember where i saw it but has lots of pictures of the process...

 

[one2dmax]

I have debated doing a seriosly big bore on the drag bike but I don't have a cooling system on that bike either. I think the math showed I could get 3000cc's or so with it. BUT, it's not practical.

The largest bore only is 1630 though 1570 leaves more sleeve thickness. The 1500 is far more practical for a street driven bike. We did do a couple of +9mm strokers but suggest +5mm as the biggest I would suggest.

The biggest bore without unshrouding the heads is 83mm (1428cc's) though I have seen (and done) with the stock heads.

We have stroked +2mm with a thicker head gasket on a stock engine/crank/rods. This created a higher compression engine without the cost of bore and pistons. The crank isn't cheap though.

Sean

 

[Rusty McNeil]

learned something new--how you stroke it matters as much as how you bore it. lol. let the jokes begin. hahaha. but seriously i'm learning so much motor theory from you folks. thanks a bunch.

Regards from my Taptalking Hercules Android

Don't rely on me for any sound theory. I'm just quoting numbers off the Internet ; )

 

[jeffro]

Ive only heard of as big as 1570,I belive that Paul(madmax) may have expairmented with bigger bores but nothing that was reliable. what kind of HP did the previous owner claim your bike to have?

He couldn't tell me lol!!! All he could rave about was how the bike would pull the front wheel through the lower gears.He was a older guy,claimed he could'nt ride it anymore cause he got vertigo .

 

[jeffro]

I think the guy is full of dog poopie....

I don't know the exact dimensions but a sleeve to handle a huge bore is eventually going to start using up room in the water jacket around the sleeve....

Stock bore is 77mm, I believe 87 is about as big as they go without getting all weird with the cases if you have the money....I think I saw a pic floating around on the internet years ago of one that had external piping to supply the water jacket....I would for sure consider that one wierd....

Without resleeving I believe 80mm is max over bore...

PCW's 1500 is 85mm over bore using stock stroke.

Mines a 1539cc's using 83mm bore and 5mm stoker crank...

I have no idea how much they can be stroked, although I think it can go more than the 5mm we went with on mine, I think the stroke can go as high as 75mm...Sean was the brains behind mine.....I just assembled it.......(and am very happy with the resultsunk

Just for grins I ran PCW's max bore of 87mm (advertised for their 1570 long rod motor) and the 5mm stroker crank I have thru a calculator and it yields 1690cc's.......

So I'd say 1690 is possible without getting really wierd with it.....:ummm: Reliability issues tho???

If you run PCW's max long rod engine bore of 87mm and Seans 75mm stroker crank thru the calculator you get 1780cc's

Of course the engine is going to cost 4 times what you paid for the bike...:rofl_200:

LOL!!! I agree with you totally there! my guess was that the bore could go only so far, the only way to be sure is to get one of those swept volume devices that measure the whole cylinder bore +stroke like the NHRA uses.I don't know where to get one of those . This guy told me he paid $4800 for it about three years earlier,he said he put 1000mi on it before parking it cause of his vertigo...

 

[jeffro]

I have debated doing a seriosly big bore on the drag bike but I don't have a cooling system on that bike either. I think the math showed I could get 3000cc's or so with it. BUT, it's not practical.

The largest bore only is 1630 though 1570 leaves more sleeve thickness. The 1500 is far more practical for a street driven bike. We did do a couple of +9mm strokers but suggest +5mm as the biggest I would suggest.

The biggest bore without unshrouding the heads is 83mm (1428cc's) though I have seen (and done) with the stock heads.

We have stroked +2mm with a thicker head gasket on a stock engine/crank/rods. This created a higher compression engine without the cost of bore and pistons. The crank isn't cheap though.

Sean

My guess is that besides yourself there would only be a handful of people across the country that could do specialized work like that,and I think the price of the bike would reflect that no matter what the age of the machine.One thing for sure everyone on here has pointed out to me is these engines have given design limits.To take them beyond that point not only is expensive, but isn't really practical outside of racing unless you want some kind of edge on the street.Would there be any practical way to measure the swept volume of one of the cylinders without taking it apart? thanks Jeff

 

[jeffro]

Sean or others may know definitivly, but I've heard of a 1700+ cc motor. It won't be long until you get your answer.
Oh and welcome to Vmax Forum. It sounds like you have a lot of work to do, just know you are in the right place to get all the help you need.

Thanks Redbone, This looks like the Vmax Mecca!!!!:worthy:

 

[one2dmax]

If you can get a bore scope we can see the tops of the pistons. Might be able to tell if it's a cast OEM type piston or a forged aftermarket unit. Might even be able to look in there with just a flashlight. A compression test will also tell you a few things. Even lifting up the cam cover and checking the cams will let you know if something has been done (they would likely not go to the trouble of a huge engine like that and not do the cams too).

Odds are he thought his was an 1800 since the gen 2's are almost 1800's.

Sean

 

[06VMAXIMUS]

Odds are he thought his was an 1800 since the gen 2's are almost 1800's.

Sean

Bingo!

 

[wildweasel_pt]

Would there be any practical way to measure the swept volume of one of the cylinders without taking it apart? thanks Jeff

You can do that by using engine oil inside the cylinder. Fill the cylinder when in BDC on the beginning of the compression stroke and turn crank to get oil out till TDC. You need a plug thread adapter with a nipple for a clear hose though. Measure the volume of oil getting out. Then you need to suck the remaining oil from the cylinder afterwords... let the engine run a bit to burn the oil remnants...

 

[one2dmax]

Good ideal Fred!

 

[jeffro]

You can do that by using engine oil inside the cylinder. Fill the cylinder when in BDC on the beginning of the compression stroke and turn crank to get oil out till TDC. You need a plug thread adapter with a nipple for a clear hose though. Measure the volume of oil getting out. Then you need to suck the remaining oil from the cylinder afterwords... let the engine run a bit to burn the oil remnants...

What would you use to measure the expended oil volume? some kind of burette or beaker?