Now 540 and running

I acquired the 2nd engine for the TT500 a while ago and the engine was rebuilt by Roger over 12 months . It’s then sat on the bench in my garage since June last year, waiting for an opportunity to get it into the bike.

The original bike had run well on the points ignition, but the spare engine’s ignition was rotten with plenty of water ingress. I’d bitten the bullet and ordered a Power Dynamo ignition unit having had some good results with a previous unit ordered for the Husqvarna Sportsman a couple of years ago. .

PowerDynamo Ignition

The new engine is also a 1T1 but has a Wiseco 4mm oversize piston, to take it to 540cc. The cams is original (something like a White Brothers cam would be nice) and the crank and conrod were good so have not been replaced, for now.

The oil feed pipes to the head has been replaced with the upgraded Kedo item , which seems like a very good idea and a weak part of the original design.

Kedo Oil Feed Pipe

The decompressor worked initially, but after the initial start, you have ease the piston over TDC before giving the bike a good wollop on the kickstart. The compression has been increased from 9:1 to 11:1. The engine sounds good and runs sweetly, and picks up nicely. Full testing needed on the track but all seems good.

Yamaha TT540

For a final flourish the front mudguard was changed as the later 1979 item was a bit big and flapped around a lot when the going was muddy.

TT500 engine work by proxy

Progress so far in the pictures below, but early stages of the strip. Cam looks okay. standard bore, but the piston a bit coked; well used engine but well looked after. Investigation work continues.




Yamaha TT500, the quick rebuild

It had taken me longer than planned, but after picking up the bike in February, it had been a stop / start affair, which had seen battles with the wheels and rims, understanding that the suppliers who service the (once) buoyant XT / TT restoration industry are a little short on facts at times, and that restoring one yourself brings the love and affection, and satisfaction.


With this little orange beauty love comes gently, and as Swiss Toni starting a TT500 is like making love to a beautiful woman. Don’t start it like a two-stroke as it will bite back. From cold, flick down the choke on the Mikuni, but keep the throttle shut. Find TDC and go just a bit further and you should manage to start it. Open the throttle and you’ll get a healthy kick back. When warm, no choke required (and no throttle).


I have replaced the vacuum Mikuni, with a standard VM34 and this made an immediate difference, probably as it was a new one from Allens Performance. For any project, getting a new carb, is a great investment and removes a lot of headaches. The ignition is still on points and I’ve heard poor feedback on some of the electronic replacements, though the Power Dynamo unit looks good, but is expensive.


Gone for road legal enduro tyres and will get an MOT later this week. Dating letter etc all done, so will hopefully be good fun on a couple of the trails. Will take it to the North Devon Atlantic MX this weekend to see how it goes. It’s not going to win anything, but should be good fun up the hill.

There are plenty of mods and engineering exercises for the TT500 and whilst there are some great Aberg HL reps etc out there, I like something original with the patina (and smell) that goes with it. Excellent.

Work on the Yamaha TT500.

The TT500 was acquired at the end of February and with the ongoing work on the Husqvarna taking priority. In March I did manage to strip the bike and start the assessing what work I needed to proiritise and what spares I needed.


The biggest issue (as it turned out) were the wheels and both front and rear rims had hairline cracks. After looking at fitting new rims (expensive) I ended up sourcing replacement rims. The front was a complete wheel obtained via eBay US, and ended up very cheap (<£80) including shipping, which was a lot less than a new rim and rebuild. For the rear, decided to respoke another good rim, so after shotblasting and painting the hub, I'd ordered some of the original Yamaha spokes from eBay. However a lot of these listed are only for XT. So, to be certain: - XT500 Rear Wheel : 1E6-25304-00 1979 Rear Spoke Set (two style of spokes) - TT500 Rear Wheel : 431-25304-01 1979 TT500 Spoke Set (3 types of spokes) The XT500 spokes are still listed by Yamaha dealers and this is the cheapest way to get them, whilst the TT500 ones are only recently (2012) discontinued. I measured up the spokes (which I'd already cut out, whoops) and sent measurements to Central Wheels and they turned out a new set of spokes within 5 days. Excellent service and they,after some shady history, should be seen as recommended suppliers.

|Type | Number of spokes | Length | Gauge|
|A|18|205mm|6 (4.87mm)|

I sent the sample spokes, which they need, and got them made in galvanized, rather than stainless.


The rest of the bike, was basically ingrained with 20-30 years of desert dirt, some of which was harder than concrete. I sanded down the frame and after toying with the idea of painting it silver, when back to my favourite Hammerite Satin Black.



For the unwary, you need to be very careful in ordering spares for TT500’s. There are a lot of people like Yuniparts, Yambits, Kedo in Germany, GPM Classics who sell replacement parts for these classic bikes; however, there listings aren’t always accurate.
– the parts for TT500 aren’t always the same as XT500; see this listing as an example.
– delivery times for plastics from most of the suppliers are long, as I think these are now all coming from Germany or the US

It’s a big business for TT500 / XT500’s, though I think the market is softening a lot more recently with a flood of TT500’s hitting the UK market, you can buy a project for < £900.

Ultrasonic Carb Cleaning : any good ?

As I’ve mentioned before on this site, getting older carbs to work well and effectively can be an uphill battle. Keyster carb kits, or a complete new VM34 Mikuni from Allens Performance can be pricey but do save a lot of buggering around and you can cut out a lot of hassle.


With both Husky WR250 and TT500 projects underway I took the advantage of working in the office with Roger to have a go with his Ultrasonic cleaner. It’s a model from Maplins, the Professional Ultrasonic Cleaner 8050-H and has a 2.5l capacity. This is slightly too small to completely submerge a decent sized motocross carb (like a VM34), but it does have a heater and programmable settings.

Not having any specific agent to put in it, we went initially for a coffee brew (a Nespresso Roma to be precise) and then for various combinations of Irn-Bru and ginger beer. The latter fizzy drinks, and I think full fat Coke would be good for this also, provoked a lot of activity in the bath.


After cleaning both carbs, some of the larger muck on the outside of the carbs was still stuck there and having a handy toothbrush along would be good. However, the slides come up really well and a regular clean will prevent throttle sticking for sure.

I’ve not tried the TT500 carb, but the VM34 on the Husky seemed improved during the brief garage-based testing. Time will tell, but a worthwhile exercise.

Yamaha TT500, a four stroke

After seeing a few TT500’s at the Telford Show this year, I found myself in Atherstone and Huggy’s Speed Shop.

Yamaha TT500 (1978)

A choice of bikes, including early and late XT’s and TT’s. Decided to plump for a later TT, with alloy swing arm and leading spindle front forks. Engine and frame numbers also matched which was nice.

More to come, as time permits.