Need recommendations for 680 kit

32 replies to this topic
  • qadsan

Posted September 28, 2005 - 07:42 PM


Make sure to check the cam chain to see if its still in spec, although Jay has probably already done that. It's good to hear everything is in good shape. The 11:1 with the stage 1 cam should make for a nice performance increase :banghead:

  • Supplicate

Posted September 29, 2005 - 08:20 AM


stage one-
cam - stage one, pipe, airbox holes, edelbrock carb
(this is the common baja 1000 set up-fast but reliable)

I've been debating on going with a new cam now for two months or so, especially since the piggy is only 6 months old in a couple days. Everything short of the cam (waiting on the edelbrock right now) is where I'm at on that list.

with that said, will a Hotcams Stage 1 (IIRC they call it the "HRC" like) require any more work internally? That is really the only thing holding me back from doing that mod, the not knowing.

  • qadsan

Posted September 29, 2005 - 09:15 AM


I like my stage 1 HotCam. It was simple to install and provided a nice bang for the buck. I wish this was the cam profile that our bikes came with stock. I'm running the stock valve train without issues. The only thing with the HotCam is you can't transfer the auto-decomp mechanism from the stock cam to the HotCam and you'll have to do without it, but that was no big deal to me and in fact it's one less thing to go wrong, less rotating mass, etc. You've still got your decomp lever which is different than the auto-decomp mechanism that was on your cam. Just make sure you're starting your bike from just past TDC as opposed to kicking it over from any postion like a 2 stroke or there's a small chance things could get ugly if the lever kicked back.

It's a pretty straight forward swap. The basics are you'll remove the old cam and pull off its cam sprocket which is pressed on. Don't pull off the cam sprocket by the ears or they'll break off. Then press the stock cam sprocket onto the HotCam and liberally coat the cam lobes with a zinc fortified engine assy lube. Install the HotCam and put your valve cover back on. Set your valve lash. Fire her up and properly break in the new cam. Enjoy!

  • Mikie1

Posted September 29, 2005 - 09:33 AM


The stage I works well with the stock compression piston. I like the Stage II for the 11:1 piston. They say it's more a mid-and-top cam, but I think you gain so much bottom with the compression change you don't feel a loss on the bottom end. The difference between the stage I and stage II is dramatic. The 680 piston makes it even more dramatic. I'm running the stage II with all OEM valvetrain components, no issues whatsoever. You do have to kick with more authority, though. Once you learn the drill it's no biggie.

  • Supplicate

Posted September 29, 2005 - 09:40 AM


You do have to kick with more authority, though.

learned to kick start motorcycles on an 83 XR-500 with an 11:1 and no decomp lever, don't think that should be an issue :banghead:

When you are talking about properly breaking in the cam, is that just similar to engine break in? Not sitting at one RPM for more then a few seconds and going through all the gears? or something more involving...

  • BWB63

Posted September 29, 2005 - 10:28 AM


680cc, 11:1, big cam without auto decompression, using the decompession lever is a must. I never used the decompression lever before. Now, if I get it wrong wow it's almost a broken leg.

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  • qadsan

Posted September 30, 2005 - 07:01 PM


...When you are talking about properly breaking in the cam, is that just similar to engine break in? Not sitting at one RPM for more then a few seconds and going through all the gears? or something more involving...

Breaking in a new cam is similar to engine break in, but different. First off you'll want to liberally coat the cam lobes with a zinc fortified engine assy lube that doesn't contain moly. Autozone sells 2oz tubes of zinc fortefied engine assembly lube (without molly) for a couple of bucks. Coating the camshaft prevents premature metal wear upon initial start up, so make sure you don't skip this step because it's important. Once you get your bike started, the most important things are not to let your bike idle and not to over rev or over load it.

If you want to be super thorough in your break in, then you'll want to run your bike on a fairly level surface (minimum load) for ~20 minutes while slowly reving it up and down the range (no big quick throttle transitions) and you're going to want to keep your engine RPM above 2,000 during this time. Then you'll want to let the bike cool down and do this same prodecure two more times so it has a total of about one hour of run time on it. Change the oil and let the bike completely cool down over night and then check your valve clearances and make adjustments if necessary. Now go tear up your town!

The most common method I've used for breaking in cams on bikes is to setup my bike with large fans blowing at the radiators. The fans need to put out some serious air because the bike will be stationary the whole time. Once the bike starts, I set my idle speed for ~3,100+ RPM so the engine RPM will NOT drop any lower than 3,000 RPM and then I'll slowly work the throttle up and down the RPM range for the next 20 to 25 minutes. Then I'll change the oil and let the engine cool down over night and check / adjust my valves if necessary and then go tear up the town.

HotCams and other cam companies usually provide break-in instructions with their cam, but the above methods is what I've typically used with good success on cars, trucks, motorcycles, etc.

  • neduro

Posted November 01, 2005 - 10:22 AM


Got the motor back, some interesting things to note.

1) We had to reject the first 2 cranks that Honda sent us for being out of spec. First one had no lateral play whatsoever at the big end and would have failed the same way as the original crank did in this motor. Second crank had been dropped or something- the rod wasn't quite straight. Third one was the charm.

2) Jay at kicks ass- very good to work with, did things right, has fantastic attention to detail. Will use him again every chance I get.

3) The finished product is amazing. Again, build was 11:1 wiseco (machined to stock piston weight), Honda wrist pin (Wiseco is not butted and very heavy = more vibes), Hotcams stage 1, port/polish head, and I threw a FMF powerbomb/Q2 on there while I had it apart. We also replaced intake valves, cam chain, and all bearings, seals and gaskets while it was apart.

As it breaks in, the motor is getting very smooth, both from the perspective of power delivery and vibes- I really like it. Had the chance to ride it next to a good running stock 650R Sunday night... the new motor is maybe a bit less strong down low, but it more than makes up for it with mid and top rush. It runs fine on pump gas.

All in all, I'm very pleased with the direction I took. For anyone looking for a low cost alternative, Jay did a great job for a reasonable amount of money and didn't just bolt it together because the parts came in- he measured everything, every time, and got it right.

  • qadsan

Posted November 01, 2005 - 01:12 PM


...We had to reject the first 2 cranks that Honda sent us for being out of spec...

That's interesting and even more interesting is that I've heard the same comments about having to reject factory Honda crank assemblies from other people as well. Hmmm....

Glad it's sorted out and I hope it lasts a long long time :banghead:

  • neduro

Posted December 05, 2005 - 01:30 PM


The stage I works well with the stock compression piston. I like the Stage II for the 11:1 piston. They say it's more a mid-and-top cam, but I think you gain so much bottom with the compression change you don't feel a loss on the bottom end.

After ~1k ish miles of prerunning for the 1000... I've decided I went the wrong way with this.

The motor does make more top end power than a stock 650... but it gives up the ability to pull itself out of deep sand low in the powerband. So what I thought would be an advantage (more linear powerband) turns out to be a drawback, because there are situations where I need to either use the clutch heavily, or shift, where the stock bike would be able to pull cleanly.

Next step is to reinstall the stock cam and see how the bike runs.

I'm also not thrilled with how the FMF exhaust fits up- it comes very close to the radiator and the frame on top, and I have to tilt the Edelbrock to clear the "powerbomb".

Live and learn, I guess.

  • Mikie1

Posted December 05, 2005 - 02:01 PM


I think you made a mistake porting and polishing the head. From what I've been told, the stock ports are too big for the stock piston and cam. Porting and polishing makes it even worse.

The additional displacement of the 680cc piston seems to make them work more efficiently; i.e., a much larger power gain than would normally be expected from just 30cc more. The Hot Cams stage II cam works awesome with the 11:1 680 piston. I used the Wiseco wrist pin and haven't had the crank re-balanced yet, so my bike does vibrate more at high revs (over about 7,500 rpm, I'd guess). Up to that point I don't notice any more vibration. So, instead of revving it higher, I just shift to the next gear and WOW! Better be hanging on.

I've gotten used to it, but the other guys who rode on my team in the 1000 said it was too much in the technical stuff. They thought the hit was a little abrupt. Might try one of those rising-rate throttle cams to make the throttle control a little easier in the slow stuff.

I'm using the FMF power bomb header (yep, it's close to the radiator and the frame, but haven't had any issues), and I had to make a small custom "dent" in the "bomb" part of the header to clear the Edelbrock squirt duration adjuster screw, but other than that it works great. I'm using a White Brothers e-meg with no end cap. Kinda loud, but not any louder than most of the other race bikes. For anything other than Baja or wide open desert, I'll run the end cap with 12 disks. Didn't have it tested, but to me it seemed quieter than the stock pipe with the HRC tip.

  • BWB63

Posted December 05, 2005 - 04:31 PM


From what David told me; (after racing the Baja 1000 on your bike) and riding my 680cc bike is yours comes on earlier harder then mine and then levels off. He thought mine kept pulling harder longer in higher RPM's. I know mine has tons more everywhere after 3,600rpm then stock but, is just more then stock at idle up to 3,600rpm. well at least with 15/47 gearing (compared to a tricked out stock bike with 14/48 gearing). It will flip the bike right over, right now in first and second and the front tire comes up real strong, fast and hard at about 3,200rpm in third no clutch. With stock gearing it's a little to much everywhere and responds a little to quickly. 14/48 At 55mph on the street, if you whack the throttle in third you will loop the bike. I run 15/49 on most trail rides, sand dunes (never use first gear in the sand) and 15/47 Desert. I have Barnum's cam (has a little more duration and more lift then the stage two cam) and 3mm oversized intake valves. I think that is what gave me a smoother, more controlable bottom end, with the on demand power in the higher RPM's. I do not have ported or polished head. If I did it over again I would use the Nikasil cylinder (not the steel sleeve) and 1mm oversized intake valves. I like Barnum's Mid Cam. Just have to know how to machine the piston, check spring bind and deck the valve guides for it

  • Mikie1

Posted December 05, 2005 - 06:30 PM


The thing I don't like about going with a cam with higher lift than the Stage II is you'd probably need to use stiffer valve springs. Plus, I haven't seen any other cams (other than Hot Cams and the HRC cam) that aren't re-grinds. I've had bad luck with re-grinds, and with re-grinds, you also have to have the rockers hardfaced. I've just seen too many failures with re-ground cams (including several of my own and my good friends').

I'm really anxious to have my crank balanced and the Carillo rod installed. Would probably be a good idea to have the piston machined to the same weight as a stock piston-- that way if I ever go back to a 650 barrel I won't have to have the crank re-done. My contact at the Honda shop here has a dyno- so can't wait to get my bike on it after I get the crank done & everything balanced well. He said he'd run it for free- he's thinking about doing the same mods to his bike (except he's running a full ProCircuit exhaust).

I also like the idea of Kibblewhite valves for durability, but not sure I'd go any bigger than stock. Would be interesting to do back-to-back dyno runs with identically-built motors except for the valves. I ride my bike mostly in the lower revs. I like a big rush of power at the crack of the throttle. I've just learned to use the clutch to moderate wheelspin in tricky situations. On slick fireroads I keep it a gear high coming out of corners & just learn to roll on the throttle instead of whacking it open.

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