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drz base gasket= race gas?

By Yamaster,
in Sport ATV

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Crazie

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You dont have to run race gas on a drz though. Doesnt it have the same compression?

There are two different versions of the DRZ. There is the S model (same EXACT motor as the Z400), and the K/E model, which has a slightly higher compression ratio.

The S model DRZ is 11.3:1 (same as the Z400), and the K/E is 12.2:1 (uses the thinner base gasket). Neither model runs on race gas, which means you'll be fine using the DRZ K/E model gasket on the LTZ. All you'll need is premium pump gas (91 octane).

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Crazie

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Yes, you can. Some people frown on this because it's "Re-using a gasket". And since the gasket is cheap in the first place, why bother.

However, if you want to give it a go, all you have to do is drill the three rivets out of the stock gasket and use the middle piece. That is the exact same piece you'd get from buying the thinner gasket....only it would be new instead of used.

People have done this mod without any problems, but because so many people frown upon it, I say do it at your own risk.

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all you have to do is drill the three rivets out of the stock gasket and use the middle piece.

The middle piece is a spacer ... if you use it ... you will be prone to leaks ... the two outside plys are the "E" base gasket. Pick the best one and use it ... The difference is the two outside plys have raised edges built into them and are the actual sealing area

On the DRZ400 I've been also splitting the head gasket on numerous bikes and using one of the outside plys ... this will achieve 13.1 compression and will run on premium pump fuel I.E. 91 octane or above ... you will FEEL the difference.

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I was with NormalZ when we did the measurements, and according to the measurements, the center piece cannot be a spacer, because it's the EXACT thickness of the "E" gasket. The two outside layers of the LTZ and "S" gaskets, are .017" when added together. Since those two layers don't add up to .010", it makes me think the outside layers are spacers. Although, I will say that we never took the center layer out, we only measured it.

Ah...I found the measurements...

The LTZ gasket is 0.027" thick. The LTZ center section of the base gasket is 0.010" thick. The upper and lower sandwich layers of the LTZ gasket are 0.0085" thick, and when combined, they are 0.017" thick. All three layers equal 0.027" thick.

It wouldn't make me feel very safe to run premium with 13:1 compression. Granted, I've heard of people doing it, but if I were running that high, I'd atleast run a lower octane race fuel or a 50/50 premium/race mix.

Are you sure you're running 13:1 though? Figuring that it takes a difference of .017" to go up .9 in compression....and half of .017" is .0085" (which is your current gasket thickness). That would only yield approx. .45 in compression by doing the math. Which would put you at 12.65:1. Unless it's not straight forward and the compression ratio increases exponentially as the gasket gets smaller. Ah....I'm just babbling anyways.

Just for curiosity sake.....how long have you been running one of those on pump gas....and have you rebuilt one that has been running like that yet?

It's good to know there are more cheap....err, I mean "Smart Thinkers" over here. :bonk:

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I was with NormalZ when we did the measurements, and according to the measurements, the center piece cannot be a spacer, because it's the EXACT thickness of the "E" gasket. The two outside layers of the LTZ and "S" gaskets, are .017" when added together. Since those two layers don't add up to .010", it makes me think the outside layers are spacers. Although, I will say that we never took the center layer out, we only measured it.

Ah...I found the measurements...

It wouldn't make me feel very safe to run premium with 13:1 compression. Granted, I've heard of people doing it, but if I were running that high, I'd atleast run a lower octane race fuel or a 50/50 premium/race mix.

Are you sure you're running 13:1 though? Figuring that it takes a difference of .017" to go up .9 in compression....and half of .017" is .0085" (which is your current gasket thickness). That would only yield approx. .45 in compression by doing the math. Which would put you at 12.65:1. Unless it's not straight forward and the compression ratio increases exponentially as the gasket gets smaller. Ah....I'm just babbling anyways.

Just for curiosity sake.....how long have you been running one of those on pump gas....and have you rebuilt one that has been running like that yet?

It's good to know there are more cheap....err, I mean "Smart Thinkers" over here. :bonk:

Trust me ... the two outside plys ARE the Same as the "E" base gasket ... I'm the guy on the DRZ400 site that is building the stroker crank along with the 94.5 bigbore ... making 475cc ... we have at least 6 of them in existance and all are running great. I just did a stroker for a guy out in kansas making a ltz475 ... One is dynoed at over 55hp ... and 40ftlbs of torque ... as far as compression ratio on the stock bore ... three of the bikes locally have been running 13.1 compression for over two years now ... Mine was one of them ... all three bike have over 15000 miles on them ... I've run as low as 89 octane fuel in mine for extended periods with no problems ... however 93 octane does seem to run better. Oh by the way all the 475cc drz that I have done locally are running 14.35 compression and still running on pump fuel ... no issues

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Crazie

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Trust me ... the two outside plys ARE the Same as the "E" base gasket ... I'm the guy on the DRZ400 site that is building the stroker crank along with the 94.5 bigbore ... making 475cc ... we have at least 6 of them in existance and all are running great. I just did a stroker for a guy out in kansas making a ltz475 ... One is dynoed at over 55hp ... and 40ftlbs of torque ... as far as compression ratio on the stock bore ... three of the bikes locally have been running 13.1 compression for over two years now ... Mine was one of them ... all three bike have over 15000 miles on them ... I've run as low as 89 octane fuel in mine for extended periods with no problems ... however 93 octane does seem to run better. Oh by the way all the 475cc drz that I have done locally are running 14.35 compression and still running on pump fuel ... no issues

Everyone has their own preference, and I'm not saying it won't work....but I'm saying I won't ever run anything over 12.5:1 on pump. I find it really hard to believe you're not getting pre-detonation on those bike with high compression and pump gas. Are you putting additives (octane boosters) in the fuel?

Also, the two outside gaskets on the LTZ are NOT equal to the "E" in thickness. As I mentioned before, myself and NormalZ measured them side by side with a micrometer. The two outside layers are .0085" each, which is .017" total. The "E" gasket is .010", which is the EXACT same as the center layer for the LTZ gasket. Those are the hard facts on the gasket, it's not a guess.

BTW, you don't need to flash your credentials to talk motors with me. I'm no expert by any means, but I've been in and out of the LTZ motor more times than I care to count.

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Everyone has their own preference, and I'm not saying it won't work....but I'm saying I won't ever run anything over 12.5:1 on pump. I find it really hard to believe you're not getting pre-detonation on those bike with high compression and pump gas. Are you putting additives (octane boosters) in the fuel?

Also, the two outside gaskets on the LTZ are NOT equal to the "E" in thickness. As I mentioned before, myself and NormalZ measured them side by side with a micrometer. The two outside layers are .0085" each, which is .017" total. The "E" gasket is .010", which is the EXACT same as the center layer for the LTZ gasket. Those are the hard facts on the gasket, it's not a guess.

BTW, you don't need to flash your credentials to talk motors with me. I'm no expert by any means, but I've been in and out of the LTZ motor more times than I care to count.

Sorry to offend you .... I'm just offering my experiences in building these engines ... In reference to the outside plys vs the "E" base gasket ... with the rib pressed into them ... it's pretty hard to get an accurate measurement ... your disputing about .0015 ... relating to compression ratio ...less than one tenth of one point ... the other point is ... you are only running one base gasket ... not stacking two (or to say another way ... just removing the center spacer). and lastly ... I have been running 13.1 compression on pump fuel WITHOUT octane boosters on multiple bikes with lots of miles for over two years now ... NO ISSUES ... Try splitting the head gasket ... what do you have to loose ... if you get fuel knock ... you are an hour and a half from putting it back to stock ... BUT ...if it works ... as it does ... you will like what you gained ...

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Crazie

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I'm not offended.....just having conversation.

Just to clarify, I'm not running any setup. I sold my Z and am still in the process of getting rid of the excess parts. I'm also not discouraging the use of the layers individually. I'm merely trying to clarify what compression ratio would be reached by doing so.

To measure the gaskets, you use the outside, not the ridges...the ridges are irrelevant. Those gaskets do not change thickness in the ridges, the ridges are simply there for sealing, and do not add or take away from the thickness of the gaskets.

As for the gasket thickness, it's very important that you understand why I'm disputing such a small difference. If you do the math, you have to take the gasket from .027" to .010" in order to go from 11.3:1 to 12.2:1 (a .9 increase in compression ratio).

Now, given that you had to decrease the base gasket by .017" to get that .9 in compression, it tells me quite a bit. For instance, half of .017" is .0085" (the same thickness as either the top or bottom layers). Because .017" only gets you .9 in compression, then .0085" (either the top or bottom layers) can only get you another .45 in compression. If you are running only one gasket (top or bottom layer) you can ONLY achieve 12.65:1 compression without shaving the head or using a custom piston. Basically, the reason I brought this up was because you can not achieve 13:1 using a stock piston and ANY combination of the stock gaskets without shaving the head.

If you were to stack, say...the two outside layers, you'd get a total gasket thickness of .017". That .017", being thicker than the "E" gasket which is .010", would actually cause you to be running less than 12.2:1.

A lot of people don't make the jump to race fuel until they are around 13:1, most racers will do it at 12.5:1 and higher. If you're only running 12.65:1 and not 13:1, then you could very well be fine running pump....and that would explain why.

How are you achieving 14.35:1 if I may ask?

Remember, I'm not questioning whether or not you are running high compression on pump gas....I'm just questioning how you are getting the compression that high.

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How are you achieving 14.35:1 if I may ask?.

It is achieved by using the 67.6 stroker crank

I figure compression by cylinder volume plus head volume at BDC. Then at TDC head volume Plus deck height converted in CC's. then ... Plus ... 0 ... or minus in CC's depending on piston top design.

I'm running a 94.5mm Wiseco 12.5 piston ... using my 67.6mm stroker crank. In my case using the bore and stroke configuration with a 12.5 piston brings the ratio to 14.35 ... running a single layer base and a single layer head gasket. Not to complicate the situation ... but before you ask ... I use a 2.5mm cylinder spacer (including the extra base gasket needed) to get back to the original stock deck height.

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NormalZ

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Oh by the way all the 475cc drz that I have done locally are running 14.35 compression and still running on pump fuel ... no issues

No way, unless that pump fuel is Sunoco 110... What's the octane of the pump fuel they're running with over 14:1 compression?

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No way, unless that pump fuel is Sunoco 110... What's the octane of the pump fuel they're running with over 14:1 compression?

93 octane ... No way to prove what it actually is ... I have to rely on what it says on the pump ... I will say this ... I took a trip out west in 1997 on a Honda Goldwing ... The gas quality out west seems to be less that what we get here in the east ... If I look around alittle bit I can find 95 octane at the pump

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