Old thread revival. I have a 1993 Trail Boss 250 and I want to switch to premixing because I think my oil pump failed. I'm currently rebuilding the top end. My first rebuild on anything.

Anyways, I wanted to confirm I have the block off procedure correct:.

1. Drain oil reservoir
2. Remove oil line attached from pump to cylinder
3. Plug oil pump line removed from cylinder
3. Plug cylinder port where oil pump line was attached
4. Premix 40:1 with a good synthetic 2 cycle oil

Can anyone confirm for me?

 

Hi Pick 'n' Strum,
This looks good if you are going to keep the oil pump installed. The only downside is that you will be running the oil pump dry so you won't be able to switch back to injection with confidence if that is a concern. But it sounds like you suspect the oil pump is bad anyway. Just be sure that the oil pump spring is good and the throttle cable is still connected to the oil pump. That will help ensure you don't run into any throttle problems.

If I was to do it over again, I would pull the oil pump and cover it with a block off kit, remove the oil reservoir, block of the oil input for the engine of course, and and get a new single pull throttle cable. I would also probably premix at 32 to 1 versus 40 to 1 to with the good synthetic oil just to be safe. Most folks including OPT would disagree with me on that. But doing all this is a lot of extra work and if this is just a putt putt machine you use around the yard or cabin, don't worry about it.

Post some pics of your machine while you're working on it and let us know if you have any other questions.

Good luck

 

Thanks for the confirmation pigseye! I do have some random follow-up questions and and update for you.

I was about to buy a blockoff kit but thought first I should try to get the old pump and drive gear out. I got the pump off but the drive gear is stuck in. I believe it's a plastic one like OPT mentioned above. Part of the drive gear rod also broke off and I think the gear is fused in there. I got out the broken piece. So now there is no contact between the pump and drive gear. An experienced person on another forum said I'm good to just throw the pump back on and of course still seal off the cylinder port. I'm absolutely not ever going to revert it back to auto inject.

The member from the other forum also advised me to go a little higher on the oil like you mention as well. He said break-in at 20:1 and then go leaner.

So my other question with this is, am I good to just seal off the oil input of the pump where the oil tank line connected to the pump? I assume there is absolutely no more interaction between pump and engine at this point.

Here is a general top end rebuild question as well: Should I pump out the oil / gas mixture in the lower end? If so, do I just refill it with my new premix? The reason I ask is in case there are any particles in the lower end since my piston was seized and I did see a lot of grooves prior to bringing the cylinder in for boring.

Just finished changing out the transmission oil tonight. I was surprised that it took good old SAE 30 per the service manual. It's apparently a type ii tranny... With everything bring so technical these days, I liked that was just a classic oil.

 

Update: Realized that the fluid in the lower end was just some of the pb blaster I sprayed to unseize the Piston. It was also much less fluid than I initially thought. I ended up getting a lot of it out with a clean rag.

Also, I did just go ahead and seal up the oil pump inlet and outlet nipples so I don't have to think about them again. Pump is back in so mainly waiting for new piston at this point. I'll probably work on a few other other small things until piston is here and cylinder is finished.

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Have an 87 cyclone that I am bringing back to life. It has the injection pump removed and blocked off. However the port under the carb boot isn’t blocked off. Could this be why the little **** won’t start? It also floods the bottom end with fuel all the time. Cleaned and rebuilt the carb, put the CORRECT carb boot on (the boot that was replaced was for a larger carb) and had a fresh top end rebuild with 125psi compression on two pulls. Has bright blue spark. What gives? Is it this oil injection port on the head?