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Uh oh.. Com test today. It looks like I did the old gal in.

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Well after my escapade with the open petcock vacuum (i mentioned in another post) I did a carb clean and plug check and got her running again but it's not a happy engine. So I did a compression check today and it looks like I've screwed the pooch. I've got a really weak 90 psi. I checked it with 2 different testers throttle open and throttle closed. Never over 90.

Truth be told the I suspect that the bike has quite a few more miles than I originally thought (and was told by the PO) and I have no idea how the previous owner maintained it. But on the plus side, I love the darn thing and don't mind putting a few more dollars into it. I can more easily afford to rebuild her a little at a time than I could afford another decent used one. That and I got the it cheap enough that it's worth a new top end without really being too upside down once she's all freshened up. Also the rest of the drive train is smooth as silk so fingers crossed on third gear.

So anyway, I guess my question is what's the most straightforward way to freshen her up? I'm guessing a valve job and piston/rings? Is it worth the effort to find a clean(er) head on e-bay? Generally how pricy is the valve work assuming that nothing is burnt or bent? Are valves available if I need one? What about Springs?

I do not (sadly) have the coin to go all out with a big bore and all the fun speed parts. I do however like the price of the high comp pistom and gasket kit at ProCycle but I don't really want to put the extra coin into the kit with the cam. Is that doable or is it necessary to use them together/

Anyway I'm down but not out. I'm really a 2 stroke guy at heart so any and all advice with these 4 stroke thingies is very much appreciated.

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The DR has a auto decompression device, so you may not have screwed the pooch.

Try a leak down test, make an addapter out of an old spark plug and fill the cylinder with commpressed air, see if it leaks out of the intake , exhaust or the engine breather, I would think you may still have carb problems.

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Shoot! Forgot about the decomp switch. Too late now I guess! :busted::banghead:

Nah just kidding actually... I was taking it apart either way since I had the paper base gasket and it was leaking pretty badly. Still it'd have been good to know weather or not my compression #'s were on or not. But considering all the miles on her I wanted a look-see inside anyway. Again any opinions and advice from the collective much appreciated and sought after. This this is one of the easiest engines I've ever turned a wrench on. Except for the 2 hidden cyl head studs front and rear it's almost a LEGO block. At this point I'm thinking a valve job (is it typical to reuse my valves if their straight?) and I'll probably pick up the high comp piston and gasket kit. Stick with the stock cam for now I guess. Anything else I need to be looking out for?

TEARDOWN4.jpg

Endgap was juuuust out of spec. It was almost 0.24

endgap.jpg

Cylinder head didn't look too bad either considering the miles.

TEARDOWN3.jpg

An I still have nice crosshatching in the bore.

TEARDOWN2.jpg

Edited by FloridaSteve

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Nothing looks to bad. All that extra fuel probably washed down the cylinder walls and help wear on the rings. If you send your cam to Web cams they will regrind your own camshaft for about half of the price of what a retailer will sell one for. I would pull the valves out of the head and inspect them and the seats, if they look good and the valve are straight I would just get some valve grinding compound and and relap them and install new valve seals.

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Really good info on the webcams. Thanks! I really like what ProCycle has to offer but the prices on some of this stuff just has me scratching my head sometimes. I build triple and twin 2 strokes bikes as my main hobby and I can get dialed in carb sets with cables and filters for what one big DR TM sells for. And the cam price has me baffled since you can get a pair of DRZ or KLR cams for the price of single reground DR cam. I know I know the cost aren't always obvious but still...

Anyway. the more I look my engine over the cleaner it's looking. I'll pull the valves tonight and see how they look. Probably clean em up and re-lap. I might even go on the cheap and just re-ring it for now till money becomes more easily available. Now that I've had her apart, the big bore kit now has me very tempted.

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I just did a rebuild on the top end of my KTM 300 EXC (2T) yesterday. Now reading this I'm beginning to get the itch to drop a HC piston and higher lift cam in the DR. I've been fighting the urge to spend any more on this bike in anticipation of Yamaha's new WR450F street legal version due out next year. I'm not so sure I'll be able to resist the urge to get into the DR's motor.

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I'm sure the WR450 will be a truly amazing ride (and for the street! Freaking WOW!) but all that performance comes with a burden of much greater complexity and cost.

For my money the DR is no slouch as an all rounder and nothing beats the simplicity of this big air cooled engine. Heck by the time I had the jug off I was laughing out lout to myself at how straightforward it was. I didn't even use a manual and it took all of 30 minutes including carefully keepin the parts and dozen or so bolts carefully sorted. The only thing easier is maybe a single cylinder 2 stroke or a flathead Briggs and Stratton.

For a few bucks you can uncork the hell out of it and STILL maintain almost unblemished reliability. Will it ever match the WR in performance. Certainly not for the average builder. But it's certainly no dog. I may break it so bad one day that I can't fix it someday but for a whole $3k or so I'll have another one off craigslist and then swap over all my goodies and just roll. Try THAT with one of the LC titanium valved high strung modern thumpers.

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No doubt the DR has significant advantages over other bikes, even those that are more expensive. I've put 26K on my 09 in the past 2 years. I've done the basic mods (pumper carb and exhaust) and I'm now at a point where I'd like a better suspension, and more power. I figure those mods are going to run me well over $1,000. I'm thinking the new Yamaha WR450F may offer all that plus less weight, wide DS tranny, reliability with reasonable PM cycles. If it’s nothing more than a plated WR450F off road version then I'd probably not be interested. I already have a high maintenance 4T don't need another.

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Yamaha's new WR450F street legal version due out next year

I wouldn't hold my breath on that one. It sure is fun to imagine though!

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Well after my escapade with the open petcock vacuum (i mentioned in another post) I did a carb clean and plug check and got her running again but it's not a happy engine. So I did a compression check today and it looks like I've screwed the pooch. I've got a really weak 90 psi. I checked it with 2 different testers throttle open and throttle closed. Never over 90.

Truth be told the I suspect that the bike has quite a few more miles than I originally thought (and was told by the PO) and I have no idea how the previous owner maintained it. But on the plus side, I love the darn thing and don't mind putting a few more dollars into it. I can more easily afford to rebuild her a little at a time than I could afford another decent used one. That and I got the it cheap enough that it's worth a new top end without really being too upside down once she's all freshened up. Also the rest of the drive train is smooth as silk so fingers crossed on third gear.

So anyway, I guess my question is what's the most straightforward way to freshen her up? I'm guessing a valve job and piston/rings? Is it worth the effort to find a clean(er) head on e-bay? Generally how pricy is the valve work assuming that nothing is burnt or bent? Are valves available if I need one? What about Springs?

I do not (sadly) have the coin to go all out with a big bore and all the fun speed parts. I do however like the price of the high comp pistom and gasket kit at ProCycle but I don't really want to put the extra coin into the kit with the cam. Is that doable or is it necessary to use them together/

Anyway I'm down but not out. I'm really a 2 stroke guy at heart so any and all advice with these 4 stroke thingies is very much appreciated.

I've got a buddy that put the hi-comp piston in with stock cam and macked out fcr carb and got a dyno pull of 46 hp. He started his mods with the piston. He got like a 4hp gain on the low end 1.75 overall. This was using stock cam and carb. So the answer to your question is yes the hi-comp piston alone does add improved performance...

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Thanks. Just what i needed. I also found the FAQ on the ProCycle site that said essentially the same thing. Same rev range but better motor for almost all of it. The new cam really opens up that RPM window. I priced just the rings and gasket set and it's only little over a hundred more for the complete piston kit so I'm sold. Order will go out tomorrow. I'm sure I'll be back with a question or two and I'll post up a report when I get cracking on it. Appreciate the help.

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Thanks. Just what i needed. I also found the FAQ on the ProCycle site that said essentially the same thing. Same rev range but better motor for almost all of it. The new cam really opens up that RPM window. I priced just the rings and gasket set and it's only little over a hundred more for the complete piston kit so I'm sold. Order will go out tomorrow. I'm sure I'll be back with a question or two and I'll post up a report when I get cracking on it. Appreciate the help.

I think we're in the same town. If your interested, I'll let you take my bike for a spin. I've got the hi-comp piston and procycle 190 cam in it. Shoot me a pm.

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I really appreciate the offer but I'm committed now anyway. Just put the order in this morning for the high comp piston/gasket kit. I'll likely send the cam in to web cams in a few paydays and get it done. with Christmas coming the carb will unfortunately have to wait so it'll be the stocker for now. Time to bump the jetting.. The piston is back ordered till Thursday though so it doesn't look like I'll have her up for the weekend anyway.

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I would go with the procycle grind before I would the web cam. Reason being the web grind loses your low and mid to give you hp at the upper end. The 223 web cam increases the duration, but keeps the stock lift. The 190 cam increases the lift and duration which although it does drop your compression ratio slightly it doesn't focus only on the upper revs, it will boost your mids and upper end. The procycle cam comes on almost like a 2 stroke when the power valve opens. The stock cam with a high comp piston will produce the most bottom end/mid power of all 3. The same guy who had the hi-comp piston and stock cam that I told you about earlier, ran the 223 for about two weeks and went back to the stock. He lives where the roads have curves and said by the time the web started making power he was shutting off for the next corner.

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That's what it seemed like looking at the #'s on the Pro-cycle page. http://www.procycle.us/info/articles/dr650/camshafts.html

The 223 cam actually has less lift than stock but wider duration The 190 had more lift and duration than both stock and 223 for what would appear to be a broader spread. For the style riding I like (even living in flat straight Florida) I'm going t give the stocker an honest run I think before dropping the money. And if it goes well I could apply the Cam money to the carb.

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