600 Weak Tranny/660 Kit

So, if I don't mod it it'll last how long? Just bought an 87 for a song and a dance, Anything a guy can do to keep it from flying apart? John

I wouldn't worry about it. I drove mine unmodified for close to 12 years without any problems. I didn't really race it and I never dropped the clutch, but I climbed a lot of hills, lugged it, and did a lot of throttle snap wheelies on the pavement which is pretty tough on it. The 660 kit and cam gave it a considerable amount of extra power, and that is when I ran into problems. So if you don't modify yours, or even just put a pipe on and jet it, I would say you would have a difficult time breaking it. A buddy of mine has had an unmodified 86 for almost as long as I have had mine with no problems. I wouldn't worry.

I had the HRC 628 kit installed in my 99 XR600 and it seems to me that the kit came with a couple of new gears.The bikes had a good 10k desert miles put on it since and it's still running great.

I seem to remember in the HRC power up kit it came with a different gear for the primary drive. I think they wanted you to change the small gear on the crank and the clutch basket which had a different gear. Doing this changed the ratios an made the tranny spin slower which in effect makes it stronger giving it more leverage against the counter shaft. Again my memory is not what it used to be. :)

Yeah you're dead right. I have just finished a master XR628 project on the last XR600 made (all red!!!). I put the following on it:

HRC628 kit - (not the closer ratio gearbox though.)

Porting and cleaning by factory Honda mechanic in Melbourne

Full (pre quiet) staintune system - headers and pipe.

Full HRC setrab triple clamp oil cooler system with XRP lines

Full CR 250 2001 front brake system and clutch controls

3 liter oil capacity

Major shaving of flywheel so beast revs far far quicker

Thumper racing pegs and easy pull throttle plate

Precision concepts gold plated forks off the 97 baja 500 XR628!!!

Precision concepts rear shock

IMS clear 17litre tank.

Standard carb rejetted - GTS reckons flat sliding is a waste of money.

OEM XR650L seat cover and plastic base matched to the last ceet hard seat foam.

Pro tapers and protaper triple clamps with 100mm bar risers.

And its red, fighting red!!!!

Took it for its first spin in the high country last November. The spread of grunt if amazing. The bike is a tractor - I sat on Big river road doing 140km/hr with major throttle to spare (14/46 rethal gearing). This motor just comes on at like 2k rpm and just keep going and going.

The thing is that it is so tiring. At the end of the day you are literally poleaxed!!!

rmhrc630- Glad you love the beast! I did a bit of hot rodding to an '88 XR6 a couple of years ago with encouraging results as well, but went a different way about it, here's what I did-

-use stock piston but head shaved 0.5mm (20 thou) to bump the compression ratio up to around 10:1.

-Staintune muffler in place of the original

-inlet port in head tidied but not altered

-jetting 168 main (165 stock), needle 3rd clip position, 62 pilot (60 stock), float level stock. DPR9-EA9 spark plug used instead of stock DPR8-EA9.

-white bros h/duty clutch springs used over stock plates.

-gearing altered to 14/46

This engine produced a fairly noticeable increase in power over another stock XR6 I had at the time, and the engine would continue to rev like the stocker except produce more power in higher rpm as the stock (light) piston was used in conjunction with the mild porting. It ran two bike lengths clear of a well jetted and piped WR400 at the time. The bike was still dead reliable and was ridden for a further 2500 kms approx of dirt riding after the mods with no problems.

At one stage I geared the bike up a little with 15/46 gearing and it pulled 155km/h top speed- much better than a stocker!

I for one would love to see some photies of those last two bikes.........sounds great!

The Honda HRC628 kit here in America was roughly $1800 last I checked and among other things, included a new primary drive gear and new clutch basket to match it.

Apparently the Honda engineers felt that the extra power and torque (25% extra according to thier lit.) required new gearing to protect the tranny.

I was the recipient of my rich buddies' stock parts that were replaced w/HRC at the dealer when his 98 was new. I followed the process and was jealous to find that his bike would run away and hide from my '94. His always ran hot though.

He proceeded to put 25,000 miles on the bike and his only failure was stripped splines on the countershaft..........too many road miles I guess.

My .02


I am curious if any one else has had simmilar problems with the power up kit or tranny problems. Also If anybody want's a go at this bike let me know.

the previous owner of my 85 600R went through two trannies in abiut 16 years (zero top ends, zero clutches) and it was basically stock (uncorked).

But there's no accounting for how he rode it. I could break my transmission tomorrow with the stock 589ccs if I really wanted to.

Also, if big bore kits tend to break trannies, why isnt it more common on 650Ls? That has more stroke to boot, which means stil more torque.

Many years ago I had a 1974 XL125 which was as dependable as a rock- play racing, trails- you couldn't hurt it. I got a Powroll 155 kit and hardweld cam, etc. The power was nearly that of my friends Suzuki TM125- it was great.

I broke probably a dozen gears over one summer- 3rd, kickstarter, and one or two others were involved. Powroll's answer to me was "try running a lighter clutch, or higher gearing". In other words undo the great power gains.

I eventually went back to a stock cylinder and piston and never had another problem! I can't believe more people don't have these problems.

Headtrauma- It's my understanding the XR650L's engine is more different to the XR6 than it looks. With different gears, shafts and primary drive ratio, and from what I can gather, they are a much more bulletproof box than the XR6. The NX650 Dominator, which was sold in oz for a fair few years, used an identical engine to the XR650L and it wasnt out of the ordinary for these engines to last well over the 40,000 km (27,000 mile) mark, much longer than an XR6.

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