302 Mod engine problem question

[modracer7b]

We had the same problem with Ken's BMH in the mid 90's. He ran a fuel pump system but it turned out to be an insufficient amount of gas tank venting. We spent a considerable amount of time on the problem and finally realized that he had gotten a different gas tank that year and as we got into the warmer part of the year the problem got worse. Probably cost him the Nationals that year as it went south coming down to the first heat start in the finals. We enlarged the vent hole and all was good again.

Bill Rosado

[bill boyes]

I had a problem once that you may the same issue. Maybe not but it is easy to check. One cylinder sleeve was low on one spot in the block. Per Bob Goller sleeves should be about .003 high so that the head gets a good squeeze on the block. Sure enough the block had about .001. And as the motor got warm water got into the cylinder. Easy to check just remove the head and gasket and lay a pocket steel 6 inch scale across the sleeves all around the bore. May not be your problem but it is easy to check.

[blueskyracer]

I have decided to do the following. I have replaced the filter and fuel line system and check the tank vent. I have cleaned the carb and replaced the O ring and corrected the cocked main needle. I have ordered a new lower crank seal and will install new rings and head to case gasket and new head gasket and different heat range of plugs and cut down the amount of oil in the fuel. I know you should only make one change at a time but these are desperate times. Two years is long enough to fight this problem..

[blueskyracer]

I would like to thank everyone for the help with this problem.. I am trying all the suggestions and I guess Daren was right two years ago that there is something wrong with this engine. I just could not believe that with the motor coming right out of the box that it could be defective. Anyway we will go thru the whole motor if I have time with the boat building project and give both boats 3 more races to get something going or maybe I will become a pit B#*#h and drink some home brew!!

[Jack Stotts]

Mike, a few years ago one of the guys in AOF was having a close problem. The engine ran fine on the beach but in the water it just would not go. We looked at everything multiple times to no avail. Finaly it was discovered that a rag that he had used to plug the pipe while in storage had slipped into the pipe. It was not visable when looking in the end because it would settle into the lager diameter area of the pipe but when started would be forced to the stinger and partially clog it. Just a thought. Know you've had many. Good luck. Keep us posted. Jack

[Team B&H]

Over the years, I've gotten much more comfortable using fixed jets rather than adjustable carburetor needle valves. Then you know exactly what you have, not some arbitrary number of "clicks" or turns. My motor, a 102 Mod, has won numerous Nationals, High Points and records often using fixed jets. Fixed jet in a Yamato you say? Yes, its easily done. Cut off the pointy end of the adjustable needle and then drill and tap the orifice for the jets of your choice. Having a Merc background and plenty of jets, I used Merc jets. The gas flowed backwards thru the jet but it worked fine. My mistake was eventually asking the MOD commission to approve the jets as an allowable modification. I figured no inspector would ever disassemble a carb to look for them but perhaps others could benefit from something similar. Of course, they wouldn't approve such a common sense change but no inspector has looked for it either.

Stotts got me thinking because I even won a Nationals in his CMH rig but it had the original adjustable needle!.

[Old Timer]

Don't forget your ignition system. I have even seen spark plugs do this.

[Team B&H]

I'll throw out one more idea. I can't tell from your pics if you have replaced the spark plug wires. I have seem at least 1 302 where this was done using a spiral core replacement wire. A bunch of the spiral core wire was unwound and then the wire inserted back into the coil. This worked for awhile but in time the very thin wire was burnt away by the continuous arcing. The motor would start and run fine on the beach but then one cylinder would cut out sometimes when loaded. Its easy to swap a different mag to try

[blueskyracer]

I'll throw out one more idea. I can't tell from your pics if you have replaced the spark plug wires. I have seem at least 1 302 where this was done using a spiral core replacement wire. A bunch of the spiral core wire was unwound and then the wire inserted back into the coil. This worked for awhile but in time the very thin wire was burnt away by the continuous arcing. The motor would start and run fine on the beach but then one cylinder would cut out sometimes when loaded. Its easy to swap a different mag to try

Still has the original plug wires where you screw on the end of the plugs to hold the wires on. It always feels like both cylinder are working but it is like a governor kicks in and only get half throttle till halfway down the straits when it takes off till I enter a corner.

[blueskyracer]

Just broke the glaze on the cylinders and put new upper rings in. I have also ordered some "V" plugs but I can already feel a lot more resistance when turning the motor over and the head is not even on. Putting the cylinder housing back on is not something I would want to do every day especially when it is 100 outside. I think it sucks!

[Aussie Steve]

Subscribed

Very interested Mike hope it is sorted for you mate

[Dave M]

Testing

Sounds like you have a turd engine. Even Merc and OMC can produce a factory turd.

If you don't get it, I suggest taking some time to go test with a Yamato know it all and sort it out. Testing meaning not at the race.

I hope you get it sorted out. Sucks when it turns out to be something you didn't do.

One more tip, check your gearbox. I have a Komato that was binding and it cost nearly 5MPH. Sent back for them to fix and it seems okay now.

[blueskyracer]

Sounds like you have a turd engine. Even Merc and OMC can produce a factory turd.

If you don't get it, I suggest taking some time to go test with a Yamato know it all and sort it out. Testing meaning not at the race.

I hope you get it sorted out. Sucks when it turns out to be something you didn't do.

One more tip, check your gearbox. I have a Komato that was binding and it cost nearly 5MPH. Sent back for them to fix and it seems okay now.

Thanks Dave, I always thought they were called lemons but TURD works. I did try a different foot with no difference. We have all day next Friday for testing so hopefully after I get the new rings broke in the motor will get out of its shell.

I just hope I can get either it or the E mod going for once. It is rough trolling in the back of the pack. As our grandson would say "It Sucks"

[Aussie Steve]

Your not putting your foot over the carb inlet buy accident mate are you

[blueskyracer]

Your not putting your foot over the carb inlet buy accident mate are you

No but I am thinking about sticking my foot up its carb!