facebook1 youtube1 twitter1 instagram google plus linkedin1 pinterest1

logosmallNOTICE:  If you are not a free registered member of the site, you will not see the photos in the forum, and you won't be able to access our premium member content. Please consider joining our community!

Welcome, Guest
Username: Password: Remember me
  • Page:
  • 1
  • 2

TOPIC: Injector pump blues

Injector pump blues 22 Mar 2019 08:39 #1

  • Luke
  • Luke's Avatar Topic Author
  • Offline
  • Novice
  • Novice
  • Posts: 48
  • Likes received: 12
So I picked up this '77 DT250 recently. Honestly, it's of the vintage where they started to get ugly, but it's growing on me. And hey, plastic doesn't rust, right? (cough cough). Really just needed something running to scratch the itch since my '74 is still in pieces, and if form follows function, the 77 is downright gorgeous by comparison. The bike is in decent shape overall, but I had only putted around a couple minutes after getting it home before figuring I'd go through it top to bottom to ensure it was reasonably safe for highway speeds. Brake shoes fore and aft, rebuilt the carb, new battery, wheel bearings, new chain, changed points and plug...hit a little snag with the rear spring, but I think I've almost got that one whooped too.

So finally I'm down to the injector pump adjustment. First thought was, "Huh, where's the starter plate?". Ok, ignore that, I'll just spin the flywheel to check stroke. Not seeing any stroke. Golly, these are probably really low geared. Spin, spin, spin, spin...nothing. Then I spotted the fuel tank leering at me from the bench. I sprang up and seized it by its Balboa Blue neck, forcing it to regurgitate into a cup. PREMIX!!! Damnit. Embarrassingly, I hadn't even bothered to ask when buying the bike. In my defense, I did check the oil tank and found it 1/3 full of purple. All the oil lines are intact and it certainly had the appearance of a functioning autolube system.

So first question, is this even the right pump for this bike? I started looking at diagrams for other years, and apparently the pumps lost their starter plates between 77 and 78. Maybe some were mixed in around the transition? Even if it were a later model pump, does that matter? Engine and frame numbers match on the bike, and it doesn't have the appearance of being frankensteined anywhere else.

And then on to fixing it (no, I don't want to premix forever). If I pull the piston away from the ramp, it springs back. Externally, everything moves freely. When I give it full throttle, there's a gap between the ramp and plate, but again, the piston never moves after much spinning. At full throttle, I can push the piston in, closing the gap, and it slooowly springs back out. Is there any other diagnosis I can attempt in place before just pulling the sucker off? Do the little plastic drive gears ever shear, or what kind of failures do these things experience? Anxious to get this blue beast on the road!
Attachments:

Please Log in or Create an account to join the conversation.

Injector pump blues 22 Mar 2019 09:27 #2

  • MarkT
  • MarkT's Avatar
  • Offline
  • Site Contributor
  • Site Contributor
  • Posts: 5386
  • Likes received: 2650
That's the right pump... I have a 76 DT175 with no primer wheel from the factory (low miles from original owner) and my 77 DT400 "barn find" that had 1000 miles on it doesn't have one either.

Parts book still shows wheel on both.

Use the oil pump bleed procedure found in the 78 DT250/400 manual supplement found in the Tech Library here... you're probably not going to see the plunger move unless the engine is running. Run the engine on premix while messing with the pump...

It would be good to pull the line off the carb (plug the carb fitting with a vacuum cap) and test for proper output at idle and with cable pulled to full output. Specs are given for output after 200 strokes of the pump which doesn't take too long with engine running.

Best would be to pull pump to send to DEET for rebuild.

Here's a link to the manual supplement... pump procedure start about page 3.

yamaha-enduros.com/index.php/workshop/se...op-manual-supplement

P.S. It won't hurt to run the bike on both pump and premix until you're sure it's fine and/or DEET goes through your pump.
The following user(s) Liked this Post: Luke

Please Log in or Create an account to join the conversation.

1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250

Injector pump blues 22 Mar 2019 10:03 #3

  • Luke
  • Luke's Avatar Topic Author
  • Offline
  • Novice
  • Novice
  • Posts: 48
  • Likes received: 12
Good info, thanks Mark. I'll see how it goes when running and hopefully see some movement. I'll hold out some slim hope that the PO was just double dipping on lube. Any idea what the overall reduction ratio is between engine revs and pump strokes? I assume it varies some by model...

Please Log in or Create an account to join the conversation.

Injector pump blues 22 Mar 2019 10:42 #4

  • MarkT
  • MarkT's Avatar
  • Offline
  • Site Contributor
  • Site Contributor
  • Posts: 5386
  • Likes received: 2650
Service manual says 43:1 for your bike.

So at 1500 rpm the pump would cycle about 35 times a minute... at idle it's a tiny movement. Pull the oil pump cable to max to finish the bleed process described in the manual and you'll see the plunger move full stroke.
The following user(s) Liked this Post: Luke

Please Log in or Create an account to join the conversation.

1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250

Injector pump blues 22 Mar 2019 10:56 #5

  • Luke
  • Luke's Avatar Topic Author
  • Offline
  • Novice
  • Novice
  • Posts: 48
  • Likes received: 12
Awesome. Thanks again. I hate asking dumb questions when they are in the manual, but I missed that one in the specs section. And just now thumbing through again I see the note in the engine overhaul section stating the old pumps had the primer wheel, but the current ones don't, and to run the motor at 2000 rpm to take place of the old primer wheel method of checking. Guess I'll have to read this sucker front to back. Some of the interesting typos and translations make it entertaining at least.

Please Log in or Create an account to join the conversation.

Injector pump blues 22 Mar 2019 20:02 #6

  • RT325
  • RT325's Avatar
  • Offline
  • Collector
  • Collector
  • Posts: 3798
  • Likes received: 1214
Just talking to myself here & i'm sure Mark has it sussed as in what to do & i've not read the story thoroughly yet.
What i"d do [not necessarily right] is let it bleed for a bit till it looks good & constant. Then run it with small pipe removed at cylinder & capped or she'll idle fast & lean. Then with it running push down on the plate, which is virtually what turning the plate does with the ramp shape. Push it down hard with two fingers & let it stroke fully & when the oil looks like good pulses out the small pipe then let the cam plate up & observe minimum stroke at a slight step at the start of the cam where the stroke plate lifts off from [by memory]. If you can see 20 thou then that's plenty. Put the pipe back on the cylinder--or carb wherever it feeds in & ride off into the sunset, Just thinking looking at ya pics now that if you need more--or less stroke then the copper washer visible under the plate can be added or subtracted. If you need to subtract then measure the options of the washers to decide which one to remove & don't loose it. Was going to say put it under the washer on the top side for later but looks like only a spring washer so might bite the copper & damage it. At work umm--55 years ago lol i had a Yamy feeler gauge with a cap on one end stacked with shims for the pump & part of normal servicing was setting the minimum stroke. Adjusting minimum stroke won't have any worthwhile bearing on what happens on full song but the cable & ramp adjustment will!!. There will be a raised mark on the cable wheel to line up with the bolt for the cable ramp. Earlier pumps had a roll pin which would fall out then i've seen them tapped in too far & stop the pump working--well it would drive the pump shaft up then it would stay up & no more pumping. Hence the started using the bolt like in yours which is stepped so it can only be screwed in to the step.
sorry, didn't mean to write an essay.
The following user(s) Liked this Post: Luke

Please Log in or Create an account to join the conversation.

Injector pump blues 22 Mar 2019 20:27 #7

  • Luke
  • Luke's Avatar Topic Author
  • Offline
  • Novice
  • Novice
  • Posts: 48
  • Likes received: 12
Thanks guys. This gives me hope it might still work and the premix was just in lieu of spending the time to bleed it properly. It's on the list for tomorrow...

Please Log in or Create an account to join the conversation.

Injector pump blues 23 Mar 2019 11:59 #8

  • Luke
  • Luke's Avatar Topic Author
  • Offline
  • Novice
  • Novice
  • Posts: 48
  • Likes received: 12
By golly it works! Bled the air, let it run a bit... Seems to be pumping fine. Haven't measured the min/max volumes yet, but after dribbling a good puddle, and with the premix still in the tank, I hooked the oil line back to the carb and went for a spin to kill all the mosquitoes in the area. Looks like I can fill er up with regular now.

Also put on my replacement mono shock. Huge difference as this one actually works. Haven't torn into the old one yet... That'll be a rainy day project.

Thanks for the help! Glad I didn't tear the pump apart thinking it was bad.
The following user(s) Liked this Post: ScottMalv

Please Log in or Create an account to join the conversation.

Injector pump blues 23 Mar 2019 16:35 #9

  • Luke
  • Luke's Avatar Topic Author
  • Offline
  • Novice
  • Novice
  • Posts: 48
  • Likes received: 12
Well it pumps.... At idle it's .5 cc's per 200 strokes. At full stroke it only goes up to 1 cc, which is way under spec. Guess I'm going to have to tear into it after all.

When holding the cam/ramp at full throttle, the plunger is not retracting all the way. It leaves probably a .040" gap between the plate and the ramp at retract.

Please Log in or Create an account to join the conversation.

Injector pump blues 23 Mar 2019 23:32 #10

  • RT325
  • RT325's Avatar
  • Offline
  • Collector
  • Collector
  • Posts: 3798
  • Likes received: 1214
Are the washers under the cap too large OD & coming down on the pump body & limiting the down stroke. I don't think they're meant to disappear down the hole a bit anyway as doesn't make sense.

Please Log in or Create an account to join the conversation.

  • Page:
  • 1
  • 2
Moderators: VinnieDEETyamadminDmanEnduronutMakotosunDevinJames Hart