A forum for owners of Yamaha TTR250 trail and enduro bikes!

Blimey Nev

You don't hang around much

Let us know how you get on with jetting please. Always interested in that stuff.

 

 

LONG OVERDUE UPDATE (And parts request )

After running it in for a few miles with the new piston and barrel, it seemed to be much more ticky than it was pre rebuild. Checked the valve clearances and they were out of spec, so new shims ordered, hoping that would solve the problem. As I took off the timing chain tensioner, it fell to pieces in my hand, which may go some way to explaining the ticking!

 

After fitting a new manual adjustment tensioner and getting the valve clearances in spec, it purred like a kitten operating a sewing machine, very satisfying. Next job on the snag list was to plumb in a wideband lambda sensor, so I could have a go at accurately tuning the carb for the bigger piston. Bung welded in the exhaust and gauge cable tied to the dash, it proved a massive help in getting the idle mix in the range, and making sure it wasn't running dangerously lean at any point.

As suggested earlier, i moved the needle clip one spot and this proved to be the best overall compromise. I haven't got it stoichiometric at WOT, but its pretty good everywhere else. Smaller main jet is probably in order, but it runs safe and pulls well with no flat spots- result. One issue I did create, though, was that at times the idle hangs high, as if the slide isn't closing properly. I took the carb apart several times and wasn't able to resolve it. Being only 3 days before departure for the trip and unlikely to be able to remedy anything if the carb rebuild didn't work, i opted to live with it for the time being. Annoying, but i could live with it.

Final job before the voyage to the Isle of Man was fitting the alloy swingarm and a shiny new Shock from Hagon suspension products as my old shock had mysteriously seized up on me. The new shock is awesome, so well worth the investment.

All jobs completed and oil changed again, it was finally time to get on the road!

If you've never been to the IOM TT, you should go, but the Isle of Man is also home to some of the most incredible trail riding Ive ever seen- almost all the byways are open to bikes, and the locals are more than happy for you to use them as intended! Out of TT season, ferry tickets are reasonably cheap and the island is very quiet, so absolutely worth getting over there if you haven't done it.

For the next 4 days we rode over 250 miles of mostly off road trails, some of which was waaaay beyond what the little TTR was supposed to be doing, but it did everything the newer KTM Enduro bikes were doing and stood up to everything like a champ, including a 20mph spill on a rutted lane after losing my way in the dust from other bikes. Lesson learned there.

Day 5 rolled round and I noticed a small oil leak that looked to be coming from the cylinder base gasket. No bother, i'll sort it when i get home, doesn't look too bad. Plenty of spare oil in my bag, no problem. Later that day it was getting worse and worse, and becoming of more of a concern...

I jumped on to ride back to camp to assess the issue further. Shortly after, as i restarted my bike after going through a gate, I heard a big crunch and noticed that the starter motor was lifting away from the engine, with quite a lot of the LHS case attached. Oh dear.

About 10 miles away from camp and with a decent amount of tools stored in the side pocket on the bike, I set about a roadside JB weld repair to get me back. I have to say, there are worse places to be broken down!

Cover off, It was immediately obvious what the issue was.

I split it in two so i could get a decent smear of JB weld around it, enough to get it back in one piece and bolted to the bike. I also removed all the starter gubbins so I wouldn't accidentally split it again!

Bodged back together and bump start later, all seemed well apart from a tiny drip every 30/40 secs.

Having happened at the end of the final day of riding, all that was left to do was the 70 mile ride back from the ferry. After a couple of interesting bump starts and one precautionary oil top up, the TTR made it home mostly intact, which is more than can be said for a couple of the newer bikes I was riding with. 

The post mortem hasn't begun yet, but i know for a fact i need:

• Starter/new shaft
• The small intermediate gear pictured above
• POSSIBLY a sprag clutch, will check that when i take it apart
• Gaskets
• Replacement LHS Engine cover

Looks like new engine covers are possible to get from Japan, but if anyone has one in the UK, or even a full engine for spares, please let me know! Overall, very pleased with how it held up given all the battering it received. Apart from the starter issue, not even a sniff of another issue all week. The 350 pulls really strong from all revs, and I really learnt a lot. Sorry for the long post!

dlee22 wrote:

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The casing looks pretty far gone to be honest but have you thought about bolting the case back on and getting the casing tig welded in a few spots, taken off the a proper job done on it? Not sure if you have any mates handy with one, seems the cheapest solution and saves another casing?

I'm sure if that had broken in a lesser developed country they wouldn't think twice about repairing it, they'd probably be successful too 😅

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 It's entirely possible to repair, no doubt, and definitely worth looking at. One of the friends I was with in IOM is handy with a TIG, but reckons its a magnesium alloy as a lot of them are. He tried welding a DRZ cover recently and it was just horrible. Is he wrong? Are they actually just regular cast ally? If so, i'd definitely consider having it welded up to save a casing and a bit of cash.

No harm in trying, I have a repaired casing in storage that look to have been welded. I purchased it cheaply on eBay as a spare but can't get to it for a year or so at a guess. Sorry I can't be any more help!

And we're back! Big thanks to everyone for help and parts. Picked up a full engine from Jamie_w which seems to be fully complete along with a load of other nice-to-have bits.

 

New generator cover and starter fitted, even managed retrieve the errant tooth from the sump!

Also fully rebuilt the carb for good measure to finally solve my idle hanging issues. Fired up first crack and now runs like an absolute dream- super quiet and more feels much tighter and responsive through the rev range.

I've also swapped the 13/52 combo for a 14/48. I felt the super short gearing was way overkill on the 350 and I was constantly reaching for the next gear. I think this works out about 13.5% difference in overall gearing, so hopefully it'll be a positive change overall. I'm sure i'll find out when it stops absolutely bucketing down! Overall, really really pleased and can't wait to get back out on it!

I think 12.5 at WOT is perfect. Check the chart in this link:

www.safrtool.com/SAFR-AFR-values.asp

Although stoich is the ideal, in real life you need to be richer in all conditions to avoid lean burn in transitions, and over heating at WOT (for eg thrashing through sand)

14/48 is a good choice I think, and your swing arm chain slider will thank you I use 14/47, mainly 'cause I'm superstitious of the even numbers combo, but for an upcoming Portugal TET I'm even considering going back to stock 14/44 because of the roadwork. She pulls it fine, will just be a bit of clutch work if the going gets technical.

Nice view from your workshop btw!

That's perfect then! Cheers for the wise words - I'm far from a carb whisperer, so I'm feeling my way round it. Certainly easy to feel when it's right and when it's not, it's nice up have that backed up by the gauge.

Went out on a few tame lanes on Sunday with a fair bit of road, the gearing is a much better compromise, especially with the extra oomph on the 350. Can comfortably do 50 now on big roads without absolutely screaming it's nuts off, and still perfectly acceptable on the technical stuff. Have to be a little more careful on great selection on the slow trails, but overall a good move I feel. I'd be more than happy doing a decent length trip like this.

I think I had a GPS confirmed 75 before it was starting to rev hard, could probably do 80 if you were less sympathetic!

And yeah, the view could definitely be worse. I'm sure all the walkers that say hello to me in the workshop must think I never ride it 😅

Good to hear that Nev! Shame Yamaha never made a TTR350 eh?

Brian

TTRfan wrote:

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Good to hear that Nev! Shame Yamaha never made a TTR350 eh?

Brian

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 Ah but if they did, would we be building TTR450s? Probably! 😂

Small update: went out at the weekend to get the last out of my current tyres before changing and the front end felt awful over the rough stuff, no compliance, almost felt like I had a flat tyre. After checking tyre pressures were okay, I figured it may be down to the forks, so when I got back I thought I'd have a look at the stanchions to see how they looked under the boots.

 

Unclipped the RHS boot and...

 

All over the front brake too! Well, at least that points a fairly obvious finger to what the problem is! I actually have a set of spare OE fork legs, so I'll rebuild those and swap them on, whilst doing steering bearings too.

Before sorting the steering bearings and forks, in the last year I have;

• Front and rear wheel bearings
• New rear shock
• OE Swingarm
• Swingarm bearings
• Linkage bearings
• New chain and sprocket
• New bars & grips
• Rebuilt front and rear callipers
• Brake pads
• Rebuilt front brake master cyl
• Rebuilt carb
• 350 rebuild
• New starter
• New engine cover
• New clutch plates

At least I know it'll be sorted soon! 

Oh, and I went Pirelli MT43 rear and Michelin Tracker front, so will see how it goes!

-- Edited by Nev on Tuesday 1st of August 2023 04:00:50 PM

-- Edited by Nev on Tuesday 1st of August 2023 04:01:55 PM

Hey Tim. No part number on that- I just called up and explained what I needed and the man from Del Monte said yes. They set it up to my weight (no pies allowed) and riding style- it seems like a great thing. It's had nearly a full year of hard riding and I've had no problems at all.

 

One advantage to the hagon shock is that it leaves a nice little gap behind the head for some kind of storage solution:

 

x1 Ali Express finest insulated flasks and one hose clamp, complete with the knob off an old pot and voila- one tool storage receptacle. The only modification required was a little retaining slot at the bottom for the standard bracket to slot into and it works a treat! Plenty room for a 1/4 socket set, a few cable ties and a small multi tool.

  

Oh, and an appropriate sticker because i'd painted it yellow and it should be a shock chamber...

Nice to see a bike with some attention lavished on it. I like your thinking with the storage solutions too!
How is the trials pattern rear tyre coping?

MT43 rear and a knobbly on the front is definitely the way to go if you are doing a reasonable amount of road work between lanes.

It's amazing how far over you can lean the TTR with that combination 

Brian

Yes Brian, I've enjoyed the combination. It's reasonably confidence inspiring. Except in this snow we've got at the moment!

Good spot on the lane Jase- it is indeed. Great little lane, we happened upon it as it's part of the TET, but we also frequented a few more lanes round Holmfirth on the return trip that were great. I'm just over the border in Lancashire these days, but I'm from Huddersfield way so do pop round there. Any decent routes or tips appreciated!