I just found this programmable TCI unit for the XT600E on the HPI.BE website..


This actually is very interesting, keeping in mind that the ignition curve on the later XT600E is pretty soft. Regulation thing no doubt.

Maybe this unit can get a few extra HP out of a XT600E ? What do you guys think?

HPI | Horse Power Ignition

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Yamaha XT600E '01, Honda XR400 '03, Yamaha XT550 '83

I looked at the web page you indicated. Looks like you can get it programmed for 2 advance curves and select either. I responded to a request for the advance curve for the 80's CDI XT600 for a guy that was buying one of the HPI's. He wanted to see if more power could be had with a better ignition curve. Sounds like a good idea, I'd order one with the stock curve and the older CDI curve and test between them to see. You certainly need to be concerned about pinging or detonation with a more advanced ignition. Perhaps even switching to the lesser advance curve if you can only get a poor grade of fuel at times.

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'84 XT600 is now bored to 2nd oversize and new OEM pistons and rings installed. No more smoking.

Thanks once again Steve for excellent info. The XT600E has nice torque but it is not that powerful. I have a honda FMX650 (basically a streetbike or semi-supermoto with the old XR650L engine). The power difference is big, once the FMX650 had been uncorcket. Touring Ted had told me all about this, and he was not wrong.


Both engines (XT600E and XR650L) are in mild trim, low compression etc.. The XT600E is one fine bike, but it would get so much better, even with only 3-5 hp more.

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Yamaha XT600E '01, Honda XR400 '03, Yamaha XT550 '83

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'84 XT600 is now bored to 2nd oversize and new OEM pistons and rings installed. No more smoking.

Claims aside, has anyone installed one? Noticeable performance improvement?
I'd like to get more pop instead pulling like a tractor.
Thanks

I think we all like more power. It can be had for a big price. Higher compression, more agressive cam timing, heavier valve spring to handle the cam, better breathing with larger valves and ports cleaned up, bigger carbs, free flowing air filter. It takes a concert of cooperating changes to achieve a sizable power increase. The down side is, shorter engine life, and just a more cantankerous bike.

I like the longevity of the current engine and can do with a little less power. We'll see how my 86 and 84 compare when they are on the road together.

Steve

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'84 XT600 is now bored to 2nd oversize and new OEM pistons and rings installed. No more smoking.

How much shorter life do you get by adding high compression piston, cam+++? I can recomend the KTM if you want action and power, with 75hp it will take on the rear wheel on all gears.

Seems like KTM has really come to the front and are really hot. I'd say a bike built to todays standards will last a long time. Materials and engineering are much improved today over 30 years ago.

Improving an old XT is not the same thing at all and may compromise the engine with mods.

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'84 XT600 is now bored to 2nd oversize and new OEM pistons and rings installed. No more smoking.

These motors are plenty stout for adding hp. All a person needs to do is put in the new oil pump that adds volume and run quality oil, changed before it breaks down from the shearing in the trans. I've had several of the 660's apart and they aren't any higher quality than the old ones (which they are designed out of). There are guys running turbos or high comp pistons, bored to the max and run at high rpms without much issues. usually problems arise from simple abuse or poor maintenance .

All motors will have somewhat shorter lives when built up however with good habits it wouldn't be a measurable difference. A person just can't let it idle for 10 minutes @350F or let the it scream at 7000rpm for 20miles just to beat or keep up with your buddy on his crotch rocket. Keep it sane and no problems.

As for the new tci running the older curve(good idea to help them out but mostly will add on top end due to more advance), welllllllll, the motors are the same, just with a starter added to one. I have an '85 jug,head,and valvetrain on my 3TB, an '89 jug & head on the 660 bottom end, all cams are the same, valves are the same, piston is the same. the trans is the biggest difference and it has nothing to do with combustion. Jetting as always will need to be tuned for proper mixture, no black magic involved. The newer heads have just a little smaller intake runners and the carb bore are smaller, there is where most of the 3-4hp loss is on those. Using the older carbs may be a good choice.

If a person wants to know where any power gains can be gotten with these motors, just ask those that installed bigger/better carbs. The stock carbs are whats holding them back, they're just a pain to change over. Then and only then will a person get all the benefits from high comp pistons , taller cam profiles, porting , timing curves, and exhausts.

Very good dissertation and explanation. As you said, good maintenance is vital and certainly much more important if the engine is taxed more. It is just amazing how much abuse these old bikes can take and still come back for more. Thank you for the good information, we all can learn from those who know...

Steve

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'84 XT600 is now bored to 2nd oversize and new OEM pistons and rings installed. No more smoking.

I have an 86 and a 90. The biggest improvement I got was from air pods and jetting up. a lot. The top end rockets with that change. I put old carbs , same pipe and jetting on the 90 and while bottom and mid improved , the timing advance kept the top end a dog. Just ordered a 90 box with the 86 curve in it from HPI. We will see what happens. Application, no guessing.THUMPTHUMP

How are your bikes at low RPM pulling, stalling etc. Back in the day, 1986 to be exact, I took my new 86 xt to Moab, stock gearing and all. I tackled the Moab Rim Trail and it just took it in stride, no stalling, just hard pulling and ledge jumping. The heart stopping was when it was time to come back down and you see how really steep it is... made it....

Steve

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'84 XT600 is now bored to 2nd oversize and new OEM pistons and rings installed. No more smoking.

Pulls like a tractor, hard to stall. It will pull clean from below idle. It took a couple of years to get the cv and conventional carb to run right with air pods I ride from sea level to about 6000 feet regularly with no issues. thumpthump

Humm, interesting. Do you have the jetting and other info to share. You have my interest.... I ride from about 1000' around Oklahoma and up to 13k in Colorado.

Steve

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'84 XT600 is now bored to 2nd oversize and new OEM pistons and rings installed. No more smoking.

On my 86, I have 86 TT 600 carbs with a 135 main in the primary carb and a 130 in the secondary. Pilot jet is a 48 . The clip in the primary carb slide needle is on the 4th down from the top. The clip in the secondary carb slide needle is on the bottom slot. Adjust the air / fuel screw to the highest idle. I am running air pods with home made outer foam covers. The pipe is a supertrapp with 12 discs. This is real rich but prevents the flat spot in mid range from running air pods on the CV secondary carb. The idle will be a little erratic until at full operating temp. The bottom and mid range will be much stronger and with the air pods the top end will take off instead of being flat. My bike will shoot up to 100 mph with no problem. be careful the old cdi has no rev limiter. Expect gas mileage to drop from 60 to 45 if running hard. MY 90 is set up the same except I have the xt carbs with the adjustable needles from a tt carb and the choke converted to a lever rather than a cable. It starts with no choke even in the winter. The bottom and mid range are great but the top is held back by the ignition curve. Thus the new box and curve. I hope for the same results as the 86. Time will tell THUMPTHUMP