Drag Racing 1978 Suzuki TS185 Nostalgia Bike

Okay, lets kick this thread off with some background information.

I recently came into possession of a custom-built 1978 Suzuki TS185-based Nostalgia Drag Bike.

The previous owner had built it over 10 years ago and raced it, so it was a simple decision to swap a bike for the drag bike and go racing. To the best of my knowledge, the bike consists of...

1. A modified TS185 frame
2. A "not sure" swingarm as I believe this model had a round pipe swingarm and this bike has a rectangular one.
3. A "not sure" rear wheel. It is a 18" rim.
4. A Yamaha(?) front wheel. It is a 21" rim.
5. The tank is custom made and holds 2 litres of fuel.
6. The seat is custom made and bolts directly to the frame.
7. Engine is a 1976 DT250
8. The Carb is a 38mm Mikuni
9. The exhaust is custom made and modified unit.
10. Forks are 33mm

I'll put more details up as this thread grows. Maybe @Murdo can give us a more detailed breakdown of the bike and how fast it ran back when he raced it?

https://www.cyclechaos.com/wiki/Suzuki_TS185

 

So, the first time I rode this bike was at the March TDRA drag meet in Gunnedah. Information about that is in here...

https://2fiftycc.com/index.php?threads/drag-racing-gunnedah-nsw.2942/page-15#post-130663

Since returning back to Melbourne, I have ordered some new tyres for the bike, but they haven't arrived yet and I'm guessing the Victorian Government doesn't consider Pablo's Tyres an essential business, so who knows when I'll get them now that the state is going into lockdown?

I have found some issues that I can try and address in the interim. The bike's engine seems to be running very rough under load and struggles to "get going" once it gets into the powerband. The engine is a DT250 unit with a YZ250 barrel and piston, so should run a similar tune to the YZ250 (1975) engine those parts came from.

When stripping the bike down I noticed there was a lot of scratching and rubbing on the inside of the chain guard. This was on both sides and the top, which seemed odd given there was plenty of room for the chain. The bike does vibrate like jack hammer, so maybe the chain was being thrown around too?



Plenty of space between the chain and the guard



Lots of rubbing



Alloy fragments on both side of the sprocket

 

Pulling the wheels off to give to Pablo's I thought I might as well check the forks and head stem. The forks are 33mm units and the caps have seen better days. The LHS cap is almost completely stuffed and getting it out may end up damaging it, so I have been searching online for a replacement (without luck).



I did find this, but it doesn't exactly look the same.



The forks may be from a 1979 TS185 as it seems to have the same progressive forks and that wheel has the same brake.

 

Pulled the carb off as part of my "get to know your bike" exercise and found the intake boot wasn't in great shape. I may have to order a new one.

 

The air filter for the 38mm Mikuni is falling apart, so I've been looking around for a suitable replacement. The existing unit looks like it's meant to be straight, but has had to be jammed against the frame rail, so I was hoping to get a unit with a bend to clear the frame rail. Failing that, I'd like to go to an airbox, but not sure how much work would be involved in trying to fit a 38mm carb into a TS185 airbox that was built for a 24mm Mikuni carb.

 

When I removed the exhaust, I accidentally took the stub piece that comes out of the barrel with the exhaust.



There was an amount of loctite grey maxx sealer around the stub, which I'll have to redo since most of it broke when I removed the exhaust. Is this normal practice or should the stub seal without the sealer?

 

When I measured the rear of the bike, I found the rear shocks were 5mm closer at the top than at the bottom where they bolt onto the swingarm. If anyone has a TS185, could you measure this for me please? The TS185 frame has a slight offset for the LHS rear shock, so there must be some reason for the shocks to be that way.

 

This only thing that Murdo changed from when he used to run the bike (before giving it to me) was the exhaust. He added a piece in to middle which seems like a reasonable amount. If anyone is or knows a 2-stroke exhaust guru, then please let me know if I should do anything like go back to the way the exhaust was previously.


You can see the piece in the middle that was added to the exhaust.


If anyone has a 1974 YZ250 exhaust, please PM me.

 

The bike has a gear-driven tacho, but it jumps around a lot, so if anyone has one laying around or knows where a good replacement (even OEM) is available, please let me know.

 

Manuals seem impossible to find, so if anyone knows where I can get a 1974 YZ250 manual, please let me know. many of the links online just take you to sites that my virus software says "No". I'm particularly interested in knowing what rev range the 1974 YZ250 had. I have a Second Generation (YZ250H) manual, but trying to get my hands in a YZ250A manual isn't working out for me.

 

Thanks Ruckus. The engine does feel like it is being "interrupted" when it should be screaming its head off over 5,000rpm. There's no feeling of any power surge in the higher rev range. I will try and find a YZ250A exhaust and measure all the vital areas. It did work before when Murdo ran it, so I might just try and go back to that shape/size and see what effect that has on the engine. I'm not a 2-stroke person, so my learning curve is steep.

 

I think that is one of the reasons Nostalgia racing is actual called "Nostalgia" racing. I love going to the big-boy drags and watching old gassers, altereds, funny cars and FED doing their thing. Brings back very fond memories. I'm looking forward to sorting this bike out as I'd like to run some reasonable times with it. It has all the ingredients to do so, we just need to get the proportions right.