The XT350 thread

[Lenz1]

Originally Posted by Zecatfish

The weakest links on the XT350 engine,
1. Timing chains are not long life items. They stretch bad. I had to replace mine at about 10k miles.
2. Timing chain tensioner.
3. Intake boots.

I've you an complete YZ490 chassis beside the shop,
I'm actually thinking about putting my XT350 engine in it,
Would solve all the weak links of the XT350 chassis.

The timing chain tensioner can be easily converted to a manual setup. Push out the roll pins that hold the tensioner together, bin the spring and locking mechanism but keep the final "actuator rod". I used a long 8mm Allen bolt / socket head to replace the spring and locking parts and ground a curved depression in the end of the socket head to match the end of the actuator rod. The threaded end of the Allen bolt passes through a new thread cut in the original tensioner housing and protrudes ~ 30 - 40mm out from the housing for adjustment.

The adjustment process now is to release the locknuts on the visible threaded section of the Allen bolt and just screw in the Allen bolt until light finger-tight only. The best confirmation of correct cam chain tension is to remove the cam cover and use a long probe to lift the chain away from the flexible tensioner / guide. If there's 5mm - 6mm of movement of the camchain away from the tensioner guide surface at mid span then it's fine.

The intake "boots" / joiners have a built-in multitude of poor engineering. Restricted internal diameters, delamination of rubber from angled manifold surfaces, rubbish materials in the rubber itself. I binned em and fabricated new pipe-based manifolds with clamped, large diameter fuel hose as the new flexible joiners.

[ahook93]

Ive got an idle problem on my 2000 350. starts cold fine, ride for a bit and the idle starts rising, the longer i ride the higher it gets. ive had it up past 3.5k.. Thought it was the carb boots because mine were cracked so I repaired them. Nothing. Figured id replace them with new ones, nothing. Bike has around 15k, ive only owned for a solid 1k now. Have had no complaints other than that and the weak suspension. Any helps appreciated.

[JensEskildsen]

What fails with the automatic camchain-tensioner? I cheked mine when I bought it, because of the stories, and checked the camchain aswell. Both were fine, and eventhough the camchain was fairly recent replaced (before I bought the bike) the motor itself have around 93.000km on it. So I guess not all are doomed from the beginning. I know I love mine.

Ahook93: A high idle when warm is almost certainly a lean condition. Try spraying starter fluid or wd40 around carb, intakeboots ect. If the idlespeed goes up/down, you've found the leakage.

[ahook93]

Originally Posted by JensEskildsen

Ahook93: A high idle when warm is almost certainly a lean condition. Try spraying starter fluid or wd40 around carb, intakeboots ect. If the idlespeed goes up/down, you've found the leakage.

ok thanks Ill check it out and see if i can find a leak. any explanation for as to why it rises higher and higher though?

[NordieBoy]

Originally Posted by Zecatfish

I've you an complete YZ490 chassis beside the shop,
I'm actually thinking about putting my XT350 engine in it,
Would solve all the weak links of the XT350 chassis.

Little bro wanted to put his TT350 engine in a modern 250F chassis.

[Zecatfish]

Assuming all goes well.
WE going to take a trip next weekend to get another XT350.
Its going to replace the DT125 the son was riding when a girl hit him.
19k miles and the price is right.
We was looking at a 2009 KLX250 but I think he would just as well off on the XT. He can use the money saved for farkles and the trip he wants to
make alone this summer when he graduates High School.

[Zecatfish]

I've got to rebuild the head on my 350.
Exhaust valves sucking oil when going down hill.
I found elsewhere that the 350 has small valves,
Has anyone sourced a larger valve for the 350?
Since I have a spare head why not go for a bit
more flow for better performance too?

[Lenz1]

Originally Posted by Zecatfish

I've got to rebuild the head on my 350.
Exhaust valves sucking oil when going down hill.
I found elsewhere that the 350 has small valves,
Has anyone sourced a larger valve for the 350?
Since I have a spare head why not go for a bit
more flow for better performance too?

Mr Le Feesh

Odd that you suggest "exhaust valves sucking oil" - why is that exactly

Changing valve sizes is a world of pain that only leads to a series of on-going engine spec changes.

Easy performance gains are available with a little careful porting and a slight rise in compression.

If 500cc power is what you're after then the cost and time effective solution is to buy a 500cc bike at the outset.

[Zecatfish]

Originally Posted by Lenz1

Mr Le Feesh

Odd that you suggest "exhaust valves sucking oil" - why is that exactly

Changing valve sizes is a world of pain that only leads to a series of on-going engine spec changes.

Easy performance gains are available with a little careful porting and a slight rise in compression.

If 500cc power is what you're after then the cost and time effective solution is to buy a 500cc bike at the outset.

Going down long grades it will start smoking, it is sucking oil past the exhaust valve seals. Then after leveling off it will continue to smoke until it burns out then is good.

[JensEskildsen]

TT350 have larger valves, dont know it the heads can be mixed and matched in some evil way. Theres only af few ponies that seperates the tt from the xt, so I dont think you'll gain much. But worth a shof if you have to replace parts anyway.

[GaMtnRider]

In what so far appears to be a futile attempt to get my XT350 suspension up to snuff, I have installed a 600lb spring on the rear shock, and the progressive springs in the front fork.

However firmer, the rear still seems to be ridiculously under-dampened and bouncy.
Changing the rear tire last night, I noticed damage to the shock shaft that was not there when I installed the spring in November.



I'm thinking this is not good.

Is there any option other than buying a used replacement shock that may or may not be any good?

[Zecatfish]

Originally Posted by GaMtnRider

In what so far appears to be a futile attempt to get my XT350 suspension up to snuff, I have installed a 600lb spring on the rear shock, and the progressive springs in the front fork.

However firmer, the rear still seems to be ridiculously under-dampened and bouncy.
Changing the rear tire last night, I noticed damage to the shock shaft that was not there when I installed the spring in November.



I'm thinking this is not good.

Is there any option other than buying a used replacement shock that may or may not be any good?

I did the 750 spring on mine, and I noticed it too.
The shock is way under-dampened with a good spring on it.
I don't think the oem shock is rebuildable but I hadn't looked into it yet either.

I was looking at some adjustable coil overs.
They was an automotive application that was fully adjustable.
It was not the cheap option, still in $350 range. But cheaper than an
aftermarket shock.

[kwakbiker]

Could you not get an eye to eye measurement and see what you can get off a newer bike that would fit via ebay(or craigslist) for a lot less. Got be worth a shot surely?

[Zecatfish]

Originally Posted by Zecatfish

I did the 750 spring on mine, and I noticed it too.
The shock is way under-dampened with a good spring on it.
I don't think the oem shock is rebuildable but I hadn't looked into it yet either.

I was looking at some adjustable coil overs.
They was an automotive application that was fully adjustable.
It was not the cheap option, still in $350 range. But cheaper than an
aftermarket shock.

Back on page 141 of this thread.
I posted a link to the shock I was thinking of.
http://www.summitracing.com/parts/HAL-DDR4955B
I never bought it but sure thought about it.....

[Lenz1]

Originally Posted by GaMtnRider

In what so far appears to be a futile attempt to get my XT350 suspension up to snuff, I have installed a 600lb spring on the rear shock, and the progressive springs in the front fork.

However firmer, the rear still seems to be ridiculously under-dampened and bouncy.
Changing the rear tire last night, I noticed damage to the shock shaft that was not there when I installed the spring in November.



I'm thinking this is not good.

Is there any option other than buying a used replacement shock that may or may not be any good?

The chroming on the rod has obviously failed but can be rebuilt. There's a company in Australia - RAD Shocky Repairs that routinely deals with rechroming etc - maybe you can find someone closer.

Discussion's I've had recently with Terry Hay in Sydney suggest a 20% - 25% increase in spring rate, front and rear for my fat arse. Call the standard bike 130kg with 55kg rider and you'd be close to the money apparently. The plan is to run ~ 15W fork oil for the front and crank up the damping on the recently rebuilt rear shock. (RAD Shocky Repairs)